Barbosa, Valmir C.
2010-01-01
Background Given an undirected graph, we consider the two problems of combinatorial optimization, which ask that its chromatic and independence numbers be found. Although both problems are NP-hard, when either one is solved on the incrementally denser graphs of a random sequence, at certain critical values of the number of edges, it happens that the transition to the next value causes optimal solutions to be obtainable substantially more easily than right before it. Methodology/Principal Findings We introduce the notion of a network's conduciveness, a probabilistically interpretable measure of how the network's structure allows it to be conducive to roaming agents, in certain conditions, from one portion of the network to another. We demonstrate that the performance jumps of graph coloring and independent sets at the critical-value transitions in the number of edges can be understood by resorting to the network that represents the solution space of the problems for each graph and examining its conduciveness between the non-optimal solutions and the optimal ones. Right past each transition, this network becomes strikingly more conducive in the direction of the optimal solutions than it was just before it, while at the same time becoming less conducive in the opposite direction. Conclusions/Significance Network conduciveness provides a useful conceptual framework for explaining the performance jumps associated with graph coloring and independent sets. We believe it may also become instrumental in helping clarify further issues related to NP-hardness that remain poorly understood. Additionally, it may become useful also in other areas in which network theory has a role to play. PMID:20628597
Barbosa, Valmir C
2010-07-08
Given an undirected graph, we consider the two problems of combinatorial optimization, which ask that its chromatic and independence numbers be found. Although both problems are NP-hard, when either one is solved on the incrementally denser graphs of a random sequence, at certain critical values of the number of edges, it happens that the transition to the next value causes optimal solutions to be obtainable substantially more easily than right before it. We introduce the notion of a network's conduciveness, a probabilistically interpretable measure of how the network's structure allows it to be conducive to roaming agents, in certain conditions, from one portion of the network to another. We demonstrate that the performance jumps of graph coloring and independent sets at the critical-value transitions in the number of edges can be understood by resorting to the network that represents the solution space of the problems for each graph and examining its conduciveness between the non-optimal solutions and the optimal ones. Right past each transition, this network becomes strikingly more conducive in the direction of the optimal solutions than it was just before it, while at the same time becoming less conducive in the opposite direction. Network conduciveness provides a useful conceptual framework for explaining the performance jumps associated with graph coloring and independent sets. We believe it may also become instrumental in helping clarify further issues related to NP-hardness that remain poorly understood. Additionally, it may become useful also in other areas in which network theory has a role to play.
Statistical mechanics of maximal independent sets
NASA Astrophysics Data System (ADS)
Dall'Asta, Luca; Pin, Paolo; Ramezanpour, Abolfazl
2009-12-01
The graph theoretic concept of maximal independent set arises in several practical problems in computer science as well as in game theory. A maximal independent set is defined by the set of occupied nodes that satisfy some packing and covering constraints. It is known that finding minimum and maximum-density maximal independent sets are hard optimization problems. In this paper, we use cavity method of statistical physics and Monte Carlo simulations to study the corresponding constraint satisfaction problem on random graphs. We obtain the entropy of maximal independent sets within the replica symmetric and one-step replica symmetry breaking frameworks, shedding light on the metric structure of the landscape of solutions and suggesting a class of possible algorithms. This is of particular relevance for the application to the study of strategic interactions in social and economic networks, where maximal independent sets correspond to pure Nash equilibria of a graphical game of public goods allocation.
Maximum independent set on diluted triangular lattices
NASA Astrophysics Data System (ADS)
Fay, C. W., IV; Liu, J. W.; Duxbury, P. M.
2006-05-01
Core percolation and maximum independent set on random graphs have recently been characterized using the methods of statistical physics. Here we present a statistical physics study of these problems on bond diluted triangular lattices. Core percolation critical behavior is found to be consistent with the standard percolation values, though there are strong finite size effects. A transfer matrix method is developed and applied to find accurate values of the density and degeneracy of the maximum independent set on lattices of limited width but large length. An extrapolation of these results to the infinite lattice limit yields high precision results, which are tabulated. These results are compared to results found using both vertex based and edge based local probability recursion algorithms, which have proven useful in the analysis of hard computational problems, such as the satisfiability problem.
Counting independent sets using the Bethe approximation
Chertkov, Michael; Chandrasekaran, V; Gamarmik, D; Shah, D; Sin, J
2009-01-01
The authors consider the problem of counting the number of independent sets or the partition function of a hard-core model in a graph. The problem in general is computationally hard (P hard). They study the quality of the approximation provided by the Bethe free energy. Belief propagation (BP) is a message-passing algorithm can be used to compute fixed points of the Bethe approximation; however, BP is not always guarantee to converge. As the first result, they propose a simple message-passing algorithm that converges to a BP fixed pont for any grapy. They find that their algorithm converges within a multiplicative error 1 + {var_epsilon} of a fixed point in {Omicron}(n{sup 2}E{sup -4} log{sup 3}(nE{sup -1})) iterations for any bounded degree graph of n nodes. In a nutshell, the algorithm can be thought of as a modification of BP with 'time-varying' message-passing. Next, they analyze the resulting error to the number of independent sets provided by such a fixed point of the Bethe approximation. Using the recently developed loop calculus approach by Vhertkov and Chernyak, they establish that for any bounded graph with large enough girth, the error is {Omicron}(n{sup -{gamma}}) for some {gamma} > 0. As an application, they find that for random 3-regular graph, Bethe approximation of log-partition function (log of the number of independent sets) is within o(1) of corret log-partition - this is quite surprising as previous physics-based predictions were expecting an error of o(n). In sum, their results provide a systematic way to find Bethe fixed points for any graph quickly and allow for estimating error in Bethe approximation using novel combinatorial techniques.
NASA Astrophysics Data System (ADS)
Takahashi, Jun; Takabe, Satoshi; Hukushima, Koji
2017-07-01
A recently proposed exact algorithm for the maximum independent set problem is analyzed. The typical running time is improved exponentially in some parameter regions compared to simple binary search. Furthermore, the algorithm overcomes the core transition point, where the conventional leaf removal algorithm fails, and works up to the replica symmetry breaking (RSB) transition point. This suggests that a leaf removal core itself is not enough for typical hardness in the random maximum independent set problem, providing further evidence for RSB being the obstacle for algorithms in general.
Optimal BLS: Optimizing transit-signal detection for Keplerian dynamics
NASA Astrophysics Data System (ADS)
Ofir, Aviv
2015-08-01
Transit surveys, both ground- and space-based, have already accumulated a large number of light curves that span several years. We optimize the search for transit signals for both detection and computational efficiencies by assuming that the searched systems can be described by Keplerian, and propagating the effects of different system parameters to the detection parameters. Importnantly, we mainly consider the information content of the transit signal and not any specific algorithm - and use BLS (Kovács, Zucker, & Mazeh 2002) just as a specific example.We show that the frequency information content of the light curve is primarily determined by the duty cycle of the transit signal, and thus the optimal frequency sampling is found to be cubic and not linear. Further optimization is achieved by considering duty-cycle dependent binning of the phased light curve. By using the (standard) BLS, one is either fairly insensitive to long-period planets or less sensitive to short-period planets and computationally slower by a significant factor of ~330 (for a 3 yr long dataset). We also show how the physical system parameters, such as the host star's size and mass, directly affect transit detection. This understanding can then be used to optimize the search for every star individually.By considering Keplerian dynamics explicitly rather than implicitly one can optimally search the transit signal parameter space. The presented Optimal BLS enhances the detectability of both very short and very long period planets, while allowing such searches to be done with much reduced resources and time. The Matlab/Octave source code for Optimal BLS is made available.
Phase transitions in Pareto optimal complex networks
NASA Astrophysics Data System (ADS)
Seoane, Luís F.; Solé, Ricard
2015-09-01
The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.
Optimal guidance for the space shuttle transition.
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1972-01-01
A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, 'E-Guidance' obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.
Optimal guidance for the space shuttle transition
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1974-01-01
A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, E-Guidance obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.
Optimal guidance for the space shuttle transition
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1972-01-01
A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, E-Guidance obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.
OTTER: An Optimized Transit Tool And Easy Reference
2016-03-01
tool , Static OTTER, is a generic, optimal solution to individual ship transit-speed combinations, in the form of a printable reference sheet that...system is in the initial stages. C. OBJECTIVES We develop a mathematical model incorporated in an Optimized Transit Tool and its Easy Reference dubbed... OPTIMIZED TRANSIT TOOL AND EASY REFERENCE by Warren Korban Blackburn March 2016 Thesis Advisor: Emily Craparo Co-Advisor: Connor McLemore
Optimized pulse sequences for suppressing unwanted transitions in quantum systems
Schroeder, C. A.; Agarwal, G. S.
2011-01-15
We investigate the nature of the pulse sequence so that unwanted transitions in quantum systems can be inhibited optimally. For this purpose we show that the sequence of pulses proposed by Uhrig [Phys. Rev. Lett. 98, 100504 (2007)] in the context of inhibition of environmental dephasing effects is optimal. We derive exact results for inhibiting the transitions and confirm the results numerically. We posit a very significant improvement by usage of the Uhrig sequence over an equidistant sequence in decoupling a quantum system from unwanted transitions. The physics of inhibition is the destructive interference between transition amplitudes before and after each pulse.
Beyond Maximum Independent Set: AN Extended Model for Point-Feature Label Placement
NASA Astrophysics Data System (ADS)
Haunert, Jan-Henrik; Wolff, Alexander
2016-06-01
Map labeling is a classical problem of cartography that has frequently been approached by combinatorial optimization. Given a set of features in the map and for each feature a set of label candidates, a common problem is to select an independent set of labels (that is, a labeling without label-label overlaps) that contains as many labels as possible and at most one label for each feature. To obtain solutions of high cartographic quality, the labels can be weighted and one can maximize the total weight (rather than the number) of the selected labels. We argue, however, that when maximizing the weight of the labeling, interdependences between labels are insufficiently addressed. Furthermore, in a maximum-weight labeling, the labels tend to be densely packed and thus the map background can be occluded too much. We propose extensions of an existing model to overcome these limitations. Since even without our extensions the problem is NP-hard, we cannot hope for an efficient exact algorithm for the problem. Therefore, we present a formalization of our model as an integer linear program (ILP). This allows us to compute optimal solutions in reasonable time, which we demonstrate for randomly generated instances.
Quantum optimal control theory applied to transitions in diatomic molecules
NASA Astrophysics Data System (ADS)
Lysebo, Marius; Veseth, Leif
2014-12-01
Quantum optimal control theory is applied to control electric dipole transitions in a real multilevel system. The specific system studied in the present work is comprised of a multitude of hyperfine levels in the electronic ground state of the OH molecule. Spectroscopic constants are used to obtain accurate energy eigenstates and electric dipole matrix elements. The goal is to calculate the optimal time-dependent electric field that yields a maximum of the transition probability for a specified initial and final state. A further important objective was to study the detailed quantum processes that take place during such a prescribed transition in a multilevel system. Two specific transitions are studied in detail. The computed optimal electric fields as well as the paths taken through the multitude of levels reveal quite interesting quantum phenomena.
Optimal Control of Transitions between Nonequilibrium Steady States
Zulkowski, Patrick R.; Sivak, David A.; DeWeese, Michael R.
2013-01-01
Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines. PMID:24386112
Optimized pulse sequences for suppressing unwanted transitions in quantum systems
NASA Astrophysics Data System (ADS)
Schroeder, C. A.; Agarwal, G. S.
2011-01-01
We investigate the nature of the pulse sequence so that unwanted transitions in quantum systems can be inhibited optimally. For this purpose we show that the sequence of pulses proposed by Uhrig [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.98.100504 98, 100504 (2007)] in the context of inhibition of environmental dephasing effects is optimal. We derive exact results for inhibiting the transitions and confirm the results numerically. We posit a very significant improvement by usage of the Uhrig sequence over an equidistant sequence in decoupling a quantum system from unwanted transitions. The physics of inhibition is the destructive interference between transition amplitudes before and after each pulse.
Optimal and robust control of transition
NASA Technical Reports Server (NTRS)
Bewley, T. R.; Agarwal, R.
1996-01-01
Optimal and robust control theories are used to determine feedback control rules that effectively stabilize a linearly unstable flow in a plane channel. Wall transpiration (unsteady blowing/suction) with zero net mass flux is used as the control. Control algorithms are considered that depend both on full flowfield information and on estimates of that flowfield based on wall skin-friction measurements only. The development of these control algorithms accounts for modeling errors and measurement noise in a rigorous fashion; these disturbances are considered in both a structured (Gaussian) and unstructured ('worst case') sense. The performance of these algorithms is analyzed in terms of the eigenmodes of the resulting controlled systems, and the sensitivity of individual eigenmodes to both control and observation is quantified.
Optimal disturbances and bypass transition in boundary layers
NASA Astrophysics Data System (ADS)
Andersson, Paul; Berggren, Martin; Henningson, Dan S.
1999-01-01
Streamwise streaks are ubiquitous in transitional boundary layers, particularly when subjected to high levels of free-stream turbulence. Using the steady boundary-layer approximation, the upstream disturbances experiencing maximum spatial energy growth are numerically calculated. The calculations use techniques commonly employed when solving optimal-control problems for distributed parameter systems. The calculated optimal disturbances consist of streamwise vortices developing into streamwise streaks. The maximum spatial energy growth was found to scale linearly with the distance from the leading edge. Based on these results, a simple model for prediction of transition location is proposed. Available experiments have been used to correlate the single constant appearing in the model.
Transition state ensemble optimization for reactions of arbitrary complexity
NASA Astrophysics Data System (ADS)
Zinovjev, Kirill; Tuñón, Iñaki
2015-10-01
In the present work, we use Variational Transition State Theory (VTST) to develop a practical method for transition state ensemble optimization by looking for an optimal hyperplanar dividing surface in a space of meaningful trial collective variables. These might be interatomic distances, angles, electrostatic potentials, etc. Restrained molecular dynamics simulations are used to obtain on-the-fly estimates of ensemble averages that guide the variations of the hyperplane maximizing the transmission coefficient. A central result of our work is an expression that quantitatively estimates the importance of the coordinates used for the localization of the transition state ensemble. Starting from an arbitrarily large set of trial coordinates, one can distinguish those that are indeed essential for the advance of the reaction. This facilitates the use of VTST as a practical theory to study reaction mechanisms of complex processes. The technique was applied to the reaction catalyzed by an isochorismate pyruvate lyase. This reaction involves two simultaneous chemical steps and has a shallow transition state region, making it challenging to define a good reaction coordinate. Nevertheless, the hyperplanar transition state optimized in the space of 18 geometrical coordinates provides a transmission coefficient of 0.8 and a committor histogram well-peaked about 0.5, proving the strength of the method. We have also tested the approach with the study of the NaCl dissociation in aqueous solution, a stringest test for a method based on transition state theory. We were able to find essential degrees of freedom consistent with the previous studies and to improve the transmission coefficient with respect to the value obtained using solely the NaCl distance as the reaction coordinate.
Preferred and Energetically Optimal Transition Speeds During Backward Human Locomotion
Hreljac, Alan; Imamura, Rodney; Escamilla, Rafael F.; Casebolt, Jeffrey; Sison, Mitell
2005-01-01
Some aspects of backward locomotion are similar to forward locomotion, while other aspects are not related to their forward counterpart. The backward preferred transition speed (BPTS) has never been directly compared to the energetically optimal transition speed (EOTS), nor has it been compared to the preferred transition speed (PTS) during forward locomotion. The purpose of this study was to determine whether the BPTS occurs at the EOTS, and to examine the relationship between the backward and forward preferred gait transition speeds. The preferred backward and forward transition speeds of 12 healthy, young subjects (7 males, 5 females) were determined after subjects were familiarized with forward and backward treadmill locomotion. On a subsequent day, subjects walked backward at speeds of 70, 80, 90, 100, and 110% of the BPTS and ran backward at speeds of 60, 75, 90, 100, and 120% of the BPTS while VO2 and RPE data were collected. After subtracting standing VO2, exercise VO2 was normalized to body mass and speed. For each subject, energy-speed curves for walking and running were fit to the normalized data points. The intersection of these curves was defined as the EOTS which was compared to the BPTS using a paired t-test (p < 0.05). RPE and VO2 at the BPTS were also compared between walking and running conditions, and the correlation between BPTS and PTS was calculated. The EOTS (1.85 ± 0.09 m·s-1) was significantly greater than the BPTS (1.63 ± 0.11 m·s-1). Even though RPE was equal for walking and running at the BPTS, VO2 was significantly greater when running. There was a strong correlation (r = 0.82) between the BPTS and the PTS. Similar to forward locomotion, the determinants of the BPTS must include factors other than metabolic energy. The gait transition during backward locomotion exhibits several similarities to its forward counterpart. Key Points The backward preferred transition speed (1.63 ± 0.11 m·s-1) was significantly less than the
Thermal conductivity switch: Optimal semiconductor/metal melting transition
NASA Astrophysics Data System (ADS)
Kim, Kwangnam; Kaviany, Massoud
2016-10-01
Scrutinizing distinct solid/liquid (s /l ) and solid/solid (s /s ) phase transitions (passive transitions) for large change in bulk (and homogenous) thermal conductivity, we find the s /l semiconductor/metal (S/M) transition produces the largest dimensionless thermal conductivity switch (TCS) figure of merit ZTCS (change in thermal conductivity divided by smaller conductivity). At melting temperature, the solid phonon and liquid molecular thermal conductivities are comparable and generally small, so the TCS requires localized electron solid and delocalized electron liquid states. For cyclic phase reversibility, the congruent phase transition (no change in composition) is as important as the thermal transport. We identify X Sb and X As (X =Al , Cd, Ga, In, Zn) and describe atomic-structural metrics for large ZTCS, then show the superiority of S/M phonon- to electron-dominated transport melting transition. We use existing experimental results and theoretical and ab initio calculations of the related properties for both phases (including the Kubo-Greenwood and Bridgman formulations of liquid conductivities). The 5 p orbital of Sb contributes to the semiconductor behavior in the solid-phase band gap and upon disorder and bond-length changes in the liquid phase this changes to metallic, creating the large contrast in thermal conductivity. The charge density distribution, electronic localization function, and electron density of states are used to mark this S/M transition. For optimal TCS, we examine the elemental selection from the transition, basic, and semimetals and semiconductor groups. For CdSb, addition of residual Ag suppresses the bipolar conductivity and its ZTCS is over 7, and for Zn3Sb2 it is expected to be over 14, based on the structure and transport properties of the better-known β -Zn4Sb3 . This is the highest ZTCS identified. In addition to the metallic melting, the high ZTCS is due to the electron-poor nature of II-V semiconductors, leading to the
Soil Vapor Extraction System Optimization, Transition, and Closure Guidance
Truex, Michael J.; Becker, Dave; Simon, Michelle A.; Oostrom, Martinus; Rice, Amy K.; Johnson, Christian D.
2013-02-08
Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. A diminishing rate of contaminant extraction over time is typically observed due to 1) diminishing contaminant mass, and/or 2) slow rates of removal for contamination in low-permeability zones. After a SVE system begins to show indications of diminishing contaminant removal rate, SVE performance needs to be evaluated to determine whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. This guidance specifically addresses the elements of this type of performance assessment. While not specifically presented, the approach and analyses in this guidance could also be applied at the onset of remediation selection for a site as a way to evaluate current or future impacts to groundwater from vadose zone contamination. The guidance presented here builds from existing guidance for SVE design, operation, optimization, and closure from the U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, and the Air Force Center for Engineering and the Environment. The purpose of the material herein is to clarify and focus on the specific actions and decisions related to SVE optimization, transition, and/or closure.
Transition Delay in Hypersonic Boundary Layers via Optimal Perturbations
NASA Technical Reports Server (NTRS)
Paredes, Pedro; Choudhari, Meelan M.; Li, Fei
2016-01-01
The effect of nonlinear optimal streaks on disturbance growth in a Mach 6 axisymmetric flow over a 7deg half-angle cone is investigated in an e ort to expand the range of available techniques for transition control. Plane-marching parabolized stability equations are used to characterize the boundary layer instability in the presence of azimuthally periodic streaks. The streaks are observed to stabilize nominally planar Mack mode instabilities, although oblique Mack mode disturbances are destabilized. Experimentally measured transition onset in the absence of any streaks correlates with an amplification factor of N = 6 for the planar Mack modes. For high enough streak amplitudes, the transition threshold of N = 6 is not reached by the Mack mode instabilities within the length of the cone, but subharmonic first mode instabilities, which are destabilized by the presence of the streaks, reach N = 6 near the end of the cone. These results suggest a passive flow control strategy of using micro vortex generators to induce streaks that would delay transition in hypersonic boundary layers.
Lundberg, Marcus; Siegbahn, Per E M
2005-05-26
Electron-transfer reactions in eight mixed-valence manganese dimers are studied using B3LYP. One of the dimers is a model of the active site of manganese catalase, while another represents a basic building block of the oxygen-evolving complex in photosystem II. The adiabatic reactions are characterized by fully optimized transition states where the single imaginary frequency represents the electron-transfer coordinate. When there is antiferromagnetic coupling between different high-spin centers, electron transfer must be accompanied by a spin transition. Spin transitions are characterized by minimum-energy crossing points between spin surfaces. Three reaction mechanisms have been investigated. First, a single-step reaction where spin flip is concerted with electron transfer. Second, an initial transition to a center with intermediate spin that can be followed by electron transfer. Third, an initial transition to a ferromagnetic state from which the electron can be transferred adiabatically. The complexes prefer the third route with rate-determining barriers ranging from 5.7 kcal/mol to 17.2 kcal/mol for different complexes. The origins of these differences are discussed in terms of oxidation states and ligand environments. Many DFT functionals overestimate charge-transfer interactions, but for the present complexes, the error should be limited because of short Mn-Mn distances.
GreedyMAX-type Algorithms for the Maximum Independent Set Problem
NASA Astrophysics Data System (ADS)
Borowiecki, Piotr; Göring, Frank
A maximum independent set problem for a simple graph G = (V,E) is to find the largest subset of pairwise nonadjacent vertices. The problem is known to be NP-hard and it is also hard to approximate. Within this article we introduce a non-negative integer valued function p defined on the vertex set V(G) and called a potential function of a graph G, while P(G) = max v ∈ V(G) p(v) is called a potential of G. For any graph P(G) ≤ Δ(G), where Δ(G) is the maximum degree of G. Moreover, Δ(G) - P(G) may be arbitrarily large. A potential of a vertex lets us get a closer insight into the properties of its neighborhood which leads to the definition of the family of GreedyMAX-type algorithms having the classical GreedyMAX algorithm as their origin. We establish a lower bound 1/(P + 1) for the performance ratio of GreedyMAX-type algorithms which favorably compares with the bound 1/(Δ + 1) known to hold for GreedyMAX. The cardinality of an independent set generated by any GreedyMAX-type algorithm is at least sum_{vin V(G)} (p(v)+1)^{-1}, which strengthens the bounds of Turán and Caro-Wei stated in terms of vertex degrees.
A numerical scheme for optimal transition paths of stochastic chemical kinetic systems
Liu Di
2008-10-01
We present a new framework for finding the optimal transition paths of metastable stochastic chemical kinetic systems with large system size. The optimal transition paths are identified to be the most probable paths according to the Large Deviation Theory of stochastic processes. Dynamical equations for the optimal transition paths are derived using the variational principle. A modified Minimum Action Method (MAM) is proposed as a numerical scheme to solve the optimal transition paths. Applications to Gene Regulatory Networks such as the toggle switch model and the Lactose Operon Model in Escherichia coli are presented as numerical examples.
Simple neural-like p systems for maximal independent set selection.
Xu, Lei; Jeavons, Peter
2013-06-01
Membrane systems (P systems) are distributed computing models inspired by living cells where a collection of processors jointly achieves a computing task. The problem of maximal independent set (MIS) selection in a graph is to choose a set of nonadjacent nodes to which no further nodes can be added. In this letter, we design a class of simple neural-like P systems to solve the MIS selection problem efficiently in a distributed way. This new class of systems possesses two features that are attractive for both distributed computing and membrane computing: first, the individual processors do not need any information about the overall size of the graph; second, they communicate using only one-bit messages.
Utilizing Maximal Independent Sets as Dominating Sets in Scale-Free Networks
NASA Astrophysics Data System (ADS)
Derzsy, N.; Molnar, F., Jr.; Szymanski, B. K.; Korniss, G.
Dominating sets provide key solution to various critical problems in networked systems, such as detecting, monitoring, or controlling the behavior of nodes. Motivated by graph theory literature [Erdos, Israel J. Math. 4, 233 (1966)], we studied maximal independent sets (MIS) as dominating sets in scale-free networks. We investigated the scaling behavior of the size of MIS in artificial scale-free networks with respect to multiple topological properties (size, average degree, power-law exponent, assortativity), evaluated its resilience to network damage resulting from random failure or targeted attack [Molnar et al., Sci. Rep. 5, 8321 (2015)], and compared its efficiency to previously proposed dominating set selection strategies. We showed that, despite its small set size, MIS provides very high resilience against network damage. Using extensive numerical analysis on both synthetic and real-world (social, biological, technological) network samples, we demonstrate that our method effectively satisfies four essential requirements of dominating sets for their practical applicability on large-scale real-world systems: 1.) small set size, 2.) minimal network information required for their construction scheme, 3.) fast and easy computational implementation, and 4.) resiliency to network damage. Supported by DARPA, DTRA, and NSF.
NASA Astrophysics Data System (ADS)
Jaskiewicz, Anna; Nowak, Andrzej S.
2006-04-01
We consider Markov control processes with Borel state space and Feller transition probabilities, satisfying some generalized geometric ergodicity conditions. We provide a new theorem on the existence of a solution to the average cost optimality equation.
Feelings of Optimism and Pessimism in Japanese Students' Transition to Junior High School.
ERIC Educational Resources Information Center
Koizumi, Reizo
1995-01-01
Generalized future expectancies of personal life success (optimism) and failure (pessimism) were examined in a cross-sectional study, with Japanese fifth- through ninth-grade students (n=584). Average optimism scores were lower and average pessimism scores were higher after the transition to junior high school. (JBJ)
Transit telescope designs optimized for multiple object spectroscopy with fibers
NASA Technical Reports Server (NTRS)
Angel, J. R. P.
1982-01-01
Instruments to simultaneously study the spectra of many objects in the field of view of a telescope can be made using fused silica fibers. The spectrograph at the 2.3m telescope of the University of Arizona has been modified for such operation, and is used routinely to study the dynamics of galaxy clusters. Consideration has been given to how the multifiber technique can best be used to obtain spectra of the many faint objects identified by deep transit survey instruments and new space and radio telescopes. A transit survey such as that planned by McGraw et al. (1980), with CCDs at the focus of a 2m transit telescope, will identify objects down to 24th magnitude, and down to 22nd magnitude will give very complete data on variability and optical energy distribution. A telescope with much larger aperture is required for spectroscopic follow up. It is suggested that large telescopes dedicated to this type of work can be made and operated for only a fraction of the cost of a general-purpose telescope.
Advanced Nuclear Fuel Cycle Transitions: Optimization, Modeling Choices, and Disruptions
NASA Astrophysics Data System (ADS)
Carlsen, Robert W.
Many nuclear fuel cycle simulators have evolved over time to help understan the nuclear industry/ecosystem at a macroscopic level. Cyclus is one of th first fuel cycle simulators to accommodate larger-scale analysis with it liberal open-source licensing and first-class Linux support. Cyclus also ha features that uniquely enable investigating the effects of modeling choices o fuel cycle simulators and scenarios. This work is divided into thre experiments focusing on optimization, effects of modeling choices, and fue cycle uncertainty. Effective optimization techniques are developed for automatically determinin desirable facility deployment schedules with Cyclus. A novel method fo mapping optimization variables to deployment schedules is developed. Thi allows relationships between reactor types and scenario constraints to b represented implicitly in the variable definitions enabling the usage o optimizers lacking constraint support. It also prevents wasting computationa resources evaluating infeasible deployment schedules. Deployed power capacit over time and deployment of non-reactor facilities are also included a optimization variables There are many fuel cycle simulators built with different combinations o modeling choices. Comparing results between them is often difficult. Cyclus flexibility allows comparing effects of many such modeling choices. Reacto refueling cycle synchronization and inter-facility competition among othe effects are compared in four cases each using combinations of fleet of individually modeled reactors with 1-month or 3-month time steps. There are noticeable differences in results for the different cases. The larges differences occur during periods of constrained reactor fuel availability This and similar work can help improve the quality of fuel cycle analysi generally There is significant uncertainty associated deploying new nuclear technologie such as time-frames for technology availability and the cost of buildin advanced reactors
NASA Astrophysics Data System (ADS)
Farano, Mirko; Cherubini, Stefania; Robinet, Jean-Christophe; De Palma, Pietro
2016-12-01
Subcritical transition in plane Poiseuille flow is investigated by means of a Lagrange-multiplier direct-adjoint optimization procedure with the aim of finding localized three-dimensional perturbations optimally growing in a given time interval (target time). Space localization of these optimal perturbations (OPs) is achieved by choosing as objective function either a p-norm (with p\\gg 1) of the perturbation energy density in a linear framework; or the classical (1-norm) perturbation energy, including nonlinear effects. This work aims at analyzing the structure of linear and nonlinear localized OPs for Poiseuille flow, and comparing their transition thresholds and scenarios. The nonlinear optimization approach provides three types of solutions: a weakly nonlinear, a hairpin-like and a highly nonlinear optimal perturbation, depending on the value of the initial energy and the target time. The former shows localization only in the wall-normal direction, whereas the latter appears much more localized and breaks the spanwise symmetry found at lower target times. Both solutions show spanwise inclined vortices and large values of the streamwise component of velocity already at the initial time. On the other hand, p-norm optimal perturbations, although being strongly localized in space, keep a shape similar to linear 1-norm optimal perturbations, showing streamwise-aligned vortices characterized by low values of the streamwise velocity component. When used for initializing direct numerical simulations, in most of the cases nonlinear OPs provide the most efficient route to transition in terms of time to transition and initial energy, even when they are less localized in space than the p-norm OP. The p-norm OP follows a transition path similar to the oblique transition scenario, with slightly oscillating streaks which saturate and eventually experience secondary instability. On the other hand, the nonlinear OP rapidly forms large-amplitude bent streaks and skips the phases
1987-08-11
A183 M FIN MCI AM NONADJACENT NUIERS ON THE CHRACTERIZRTION OF FIBONACCI MU.. (U) GEORGIA UNIV ATHENS DEPT OF CNENISTRY S EL-IASIL 11 AUG 67 TR-50...Code 4007001-6 0Technical Report No. 50 Fibonacci and Nonadjacent Numbers On the Characterization of Fibonacci Numbers as Maximal Independent Sets of...aide It necessary and Identify’ by block nuinbet) Graph Theory Fibonacci Numbers Nonadjacent Numbers King Patterns 15anzen inWdrnrarhnnc 20r ANSTRAC lCni
Transitions in optimal adaptive strategies for populations in fluctuating environments
NASA Astrophysics Data System (ADS)
Mayer, Andreas; Mora, Thierry; Rivoire, Olivier; Walczak, Aleksandra M.
2017-09-01
Biological populations are subject to fluctuating environmental conditions. Different adaptive strategies can allow them to cope with these fluctuations: specialization to one particular environmental condition, adoption of a generalist phenotype that compromises between conditions, or population-wise diversification (bet hedging). Which strategy provides the largest selective advantage in the long run depends on the range of accessible phenotypes and the statistics of the environmental fluctuations. Here, we analyze this problem in a simple mathematical model of population growth. First, we review and extend a graphical method to identify the nature of the optimal strategy when the environmental fluctuations are uncorrelated. Temporal correlations in environmental fluctuations open up new strategies that rely on memory but are mathematically challenging to study: We present analytical results to address this challenge. We illustrate our general approach by analyzing optimal adaptive strategies in the presence of trade-offs that constrain the range of accessible phenotypes. Our results extend several previous studies and have applications to a variety of biological phenomena, from antibiotic resistance in bacteria to immune responses in vertebrates.
Optimal network modification for spectral radius dependent phase transitions
NASA Astrophysics Data System (ADS)
Rosen, Yonatan; Kirsch, Lior; Louzoun, Yoram
2016-09-01
The dynamics of contact processes on networks is often determined by the spectral radius of the networks adjacency matrices. A decrease of the spectral radius can prevent the outbreak of an epidemic, or impact the synchronization among systems of coupled oscillators. The spectral radius is thus tightly linked to network dynamics and function. As such, finding the minimal change in network structure necessary to reach the intended spectral radius is important theoretically and practically. Given contemporary big data resources such as large scale communication or social networks, this problem should be solved with a low runtime complexity. We introduce a novel method for the minimal decrease in weights of edges required to reach a given spectral radius. The problem is formulated as a convex optimization problem, where a global optimum is guaranteed. The method can be easily adjusted to an efficient discrete removal of edges. We introduce a variant of the method which finds optimal decrease with a focus on weights of vertices. The proposed algorithm is exceptionally scalable, solving the problem for real networks of tens of millions of edges in a short time.
Parameter optimization for transitions between memory states in small arrays of Josephson junctions
NASA Astrophysics Data System (ADS)
Rezac, J. D.; Imam, N.; Braiman, Y.
2017-05-01
Coupled arrays of Josephson junctions possess multiple stable zero voltage states. Such states can store information and consequently can be utilized for cryogenic memory applications. Basic memory operations can be implemented by sending a pulse to one of the junctions and studying transitions between the states. In order to be suitable for memory operations, such transitions between the states have to be fast and energy efficient. In this paper we employed simulated annealing, a stochastic optimization algorithm, to study parameter optimization of array parameters which minimizes times and energies of transitions between specifically chosen states that can be utilized for memory operations (Read, Write, and Reset). Simulation results show that such transitions occur with access times on the order of 10-100 ps and access energies on the order of 10-19-5×10-18 J. Numerical simulations are validated with approximate analytical results.
Optimal precursor of the transition from Kuroshio large meander to straight path
NASA Astrophysics Data System (ADS)
Wang, Qiang; Ma, Libin; Xu, Qiangqiang
2013-09-01
We used the conditional nonlinear optimal perturbation (CNOP) method to explore the optimal precursor of the transition from Kuroshio large meander (LM) to straight path within a barotropic inflowout-flow model, and found that large amplitudes of the optimal precursor are mainly located in the east of Kyushu, which implies that perturbations in the region are important for the transition from LM to straight path. Furthermore, we investigated the transition processes caused by the optimal precursor, and found that these processes could be divided into three stages. In the first stage, a cyclonic eddy is advected to the formation region of the Kuroshio large meander, which enhances the LM path and causes a cyclonic eddy to shed from the Kuroshio mainstream. This process causes the LM path to change into a small meander path. Subsequently, the small meander is maintained for a period because the vorticity advection is balanced by the beta effect in the second stage. In the third stage, the small meander weakens and the straight path ultimately forms. The positive vorticity advecting downstream is responsible for this process. The exploration of the optimal precursor will conduce to improve the prediction of the transition processes from LM path to straight path, and its spatial structure can be used to guide Kuroshio targeted observation studies.
Optimal Control of Markov Processes with Age-Dependent Transition Rates
Ghosh, Mrinal K. Saha, Subhamay
2012-10-15
We study optimal control of Markov processes with age-dependent transition rates. The control policy is chosen continuously over time based on the state of the process and its age. We study infinite horizon discounted cost and infinite horizon average cost problems. Our approach is via the construction of an equivalent semi-Markov decision process. We characterise the value function and optimal controls for both discounted and average cost cases.
Phase transitions and optimal transport in stochastic roundabout traffic
NASA Astrophysics Data System (ADS)
Foulaadvand, M. Ebrahim; Maass, Philipp
2016-07-01
We study traffic in a roundabout model, where the dynamics along the interior lane of the roundabout are described by the totally asymmetric simple exclusion process (TASEP). Vehicles can enter the interior lane or exit from it via S intersecting streets with given rates, and locally modified dynamics at the junctions take into account that collisions of entering vehicles with vehicles approaching the entrance point from the interior lane should be avoided. A route matrix specifies the probabilities for vehicles to arrive from and to exit to certain intersecting streets. By subdividing the interior lane into segments between consecutive intersecting streets with effective entrance and exit rates, a classification of the stationary roundabout traffic in terms of TASEP multiphases is given, where each segment can be in either the low-density, high-density, or maximum current TASEP phase. A general methodology is developed, which allows one to calculate the multiphases and optimal throughput conditions based on a mean-field treatment. Explicit analytical results from this treatment are derived for equivalent interesting streets. The results are shown to be in good agreement with kinetic Monte Carlo simulations.
Phase transitions and optimal transport in stochastic roundabout traffic.
Foulaadvand, M Ebrahim; Maass, Philipp
2016-07-01
We study traffic in a roundabout model, where the dynamics along the interior lane of the roundabout are described by the totally asymmetric simple exclusion process (TASEP). Vehicles can enter the interior lane or exit from it via S intersecting streets with given rates, and locally modified dynamics at the junctions take into account that collisions of entering vehicles with vehicles approaching the entrance point from the interior lane should be avoided. A route matrix specifies the probabilities for vehicles to arrive from and to exit to certain intersecting streets. By subdividing the interior lane into segments between consecutive intersecting streets with effective entrance and exit rates, a classification of the stationary roundabout traffic in terms of TASEP multiphases is given, where each segment can be in either the low-density, high-density, or maximum current TASEP phase. A general methodology is developed, which allows one to calculate the multiphases and optimal throughput conditions based on a mean-field treatment. Explicit analytical results from this treatment are derived for equivalent interesting streets. The results are shown to be in good agreement with kinetic Monte Carlo simulations.
NASA Astrophysics Data System (ADS)
Hocker, David; Yan, Julia; Rabitz, Herschel
2016-05-01
Bose-Einstein condensates (BECs) offer the potential to examine quantum behavior at large length and time scales, as well as forming promising candidates for quantum technology applications. Thus, the manipulation of BECs using control fields is a topic of prime interest. We consider BECs in the mean-field model of the Gross-Pitaevskii equation (GPE), which contains linear and nonlinear features, both of which are subject to control. In this work we report successful optimal control simulations of a one-dimensional GPE by modulation of the linear and nonlinear terms to stimulate transitions into excited coherent modes. The linear and nonlinear controls are allowed to freely vary over space and time to seek their optimal forms. The determination of the excited coherent modes targeted for optimization is numerically performed through an adaptive imaginary time propagation method. Numerical simulations are performed for optimal control of mode-to-mode transitions between the ground coherent mode and the excited modes of a BEC trapped in a harmonic well. The results show greater than 99 % success for nearly all trials utilizing reasonable initial guesses for the controls, and analysis of the optimal controls reveals primarily direct transitions between initial and target modes. The success of using solely the nonlinearity term as a control opens up further research toward exploring novel control mechanisms inaccessible to linear Schrödinger-type systems.
Ding, Junjia; Ade, P. A. R.; Anderson, A. J.; ...
2016-12-15
In this study, we describe the optimization of transition-edge-sensor (TES) detector arrays for the thirdgeneration camera for the South PoleTelescope.The camera,which contains ~16 000 detectors, will make high-angular-resolution maps of the temperature and polarization of the cosmic microwave background. Our key results are scatter in the transition temperature of Ti/Au TESs is reduced by fabricating the TESs on a thin Ti(5 nm)/Au(5 nm) buffer layer and the thermal conductivity of the legs that support our detector islands is dominated by the SiOx dielectric in the microstrip transmission lines that run along
Ding, Junjia; Ade, P. A. R.; Anderson, A. J.; ...
2016-12-15
In this study, we describe the optimization of transition-edge-sensor (TES) detector arrays for the thirdgeneration camera for the South PoleTelescope.The camera,which contains ~16 000 detectors, will make high-angular-resolution maps of the temperature and polarization of the cosmic microwave background. Our key results are scatter in the transition temperature of Ti/Au TESs is reduced by fabricating the TESs on a thin Ti(5 nm)/Au(5 nm) buffer layer and the thermal conductivity of the legs that support our detector islands is dominated by the SiOx dielectric in the microstrip transmission lines that run along
Optimization of film synthesized rare earth transition metal permanent magnet systems
Cadieu, F.J.
1990-01-01
This report reviews work on the optimization of film synthesized rare earth transition metal permanent magnet systems. Topics include: high coercivity in Sm-Fe-Ti-V, Sm-Fe-V, and two element systems; ThMn{sub 12} type pseudobinary SmFe{sub 12 {minus} X}T{sub X}; and sputter process control for the synthesis of precisely textured RE-TM magnetic films. (JL)
Bayesian optimization of perfusion and transit time estimation in PASL-MRI.
Santos, Nuno; Sanches, João; Figueiredo, Patrícia
2010-01-01
Pulsed Arterial Spin Labeling (PASL) techniques potentially allow the absolute, non-invasive quantification of brain perfusion and arterial transit time. This can be achieved by fitting a kinetic model to the data acquired at a number of inversion time points (TI). The intrinsically low SNR of PASL data, together with the uncertainty in the model parameters, can hinder the estimation of the parameters of interest. Here, a two-compartment kinetic model is used to estimate perfusion and transit time, based on a Maximum a Posteriori (MAP) criterion. A priori information concerning the physiological variation of the multiple model parameters is used to guide the solution. Monte Carlo simulations are performed to compare the accuracy of our proposed Bayesian estimation method with a conventional Least Squares (LS) approach, using four different sets of TI points. Each set is obtained either with a uniform distribution or an optimal sampling strategy designed based on the same MAP criterion. We show that the estimation errors are minimized when our proposed Bayesian estimation method is employed in combination with an optimal set of sampling points. In conclusion, our results indicate that PASL perfusion and transit time measurements would benefit from a Bayesian approach for the optimization of both the sampling strategy and the estimation algorithm, whereby prior information on the parameters is used.
Cianchetti, Flor A.
2010-01-01
Moving our fingertips toward objects to produce well-directed forces immediately upon contact is fundamental to dexterous manipulation. This apparently simple motion-to-force transition in fact involves a time-critical, predictive switch in control strategy. Given that dexterous manipulation must accommodate multiple mechanical conditions, we investigated whether and how this transition adapts to task difficulty. Eight adults (19–39 yr) produced ramps of isometric vertical fingertip force against a rigid surface immediately following a tapping motion. By changing target surface friction and size, we defined an easier (sandpaper, 11 mm diam) versus a more difficult (polished steel, 5 mm diam) task. As in prior work, we assembled fine-wire electromyograms from all seven muscles of the index finger into a seven-dimensional vector defining the full muscle coordination pattern—and quantified its temporal evolution as its alignment with a reference coordination pattern vector for steady-state force production. As predicted by numerical optimizations to neuromuscular delays, our empirical and sigmoidal nonlinear regression analyses show that the coordination pattern transitions begin sooner for the more difficult tasks than for the easier tasks (∼120 ms, P < 0.02, and ∼115 ms, P < 0.015, respectively) and that the coordination pattern transition in alignment is well represented by a sigmoidal trend (R^2 > 0.7 in most cases). Importantly, the force vector following contact had smaller directional error (P < 0.02) for the more difficult task even though the transition in coordination pattern was less stereotypical and uniform than for the easier task. These adaptations of transition strategy to task difficulty are compatible with an optimization to counteract neuromuscular delays and noise to enable this fundamental element of dexterous manipulation. PMID:19889857
Nonlinear optimal control of bypass transition in a boundary layer flow
NASA Astrophysics Data System (ADS)
Xiao, Dandan; Papadakis, George
2017-05-01
The central aim of the paper is to apply and assess a nonlinear optimal control strategy to suppress bypass transition, due to bimodal interactions [T. A. Zaki and P. A. Durbin, "Mode interaction and the bypass route to transition," J. Fluid Mech. 531, 85 (2005)] in a zero-pressure-gradient boundary layer. To this end, a Lagrange variational formulation is employed that results in a set of adjoint equations. The optimal wall actuation (blowing and suction from a control slot) is found by solving iteratively the nonlinear Navier-Stokes and the adjoint equations in a forward/backward loop using direct numerical simulation. The optimization is performed in a finite time horizon. Large values of optimization horizon result in the instability of the adjoint equations. The control slot is located exactly in the region of transition. The results show that the control is able to significantly reduce the objective function, which is defined as the spatial and temporal integral of the quadratic deviation from the Blasius profile plus a term that quantifies the control cost. The physical mechanism with which the actuation interacts with the flow field is investigated and analysed in relation to the objective function employed. Examination of the joint probability density function shows that the control velocity is correlated with the streamwise velocity in the near wall region but this correlation is reduced as time elapses. The spanwise averaged velocity is distorted by the control action, resulting in a significant reduction of the skin friction coefficient. Results are presented with and without zero-net mass flow constraint of the actuation velocity. The skin friction coefficient drops below the laminar value if there is no mass constraint; it remains however larger than laminar when this constraint is imposed. Results are also compared with uniform blowing using the same time-average velocity obtained from the nonlinear optimal algorithm.
Keyong Li; Seong-Cheol Kang; I. Ch. Paschalidis
2007-09-01
This paper investigates stochastic processes that are modeled by a finite number of states but whose transition probabilities are uncertain and possibly time-varying. The treatment of uncertain transition probabilities is important because there appears to be a disconnection between the practice and theory of stochastic processes due to the difficulty of assigning exact probabilities to real-world events. Also, when the finite-state process comes as a reduced model of one that is more complicated in nature (possibly in a continuous state space), existing results do not facilitate rigorous analysis. Two approaches are introduced here. The first focuses on processes with one terminal state and the properties that affect their convergence rates. When a process is on a complicated graph, the bound of the convergence rate is not trivially related to that of the probabilities of individual transitions. Discovering the connection between the two led us to define two concepts which we call 'progressivity' and 'sortedness', and to a new comparison theorem for stochastic processes. An optimality criterion for robust optimal control also derives from this comparison theorem. In addition, this result is applied to the case of mission-oriented autonomous robot control to produce performance estimate within a control framework that we propose. The second approach is in the MDP frame work. We will introduce our preliminary work on optimistic robust optimization, which aims at finding solutions that guarantee the upper bounds of the accumulative discounted cost with prescribed probabilities. The motivation here is to address the issue that the standard robust optimal solution tends to be overly conservative.
Utilizing Direct Numerical Simulations of Transition and Turbulence in Design Optimization
NASA Technical Reports Server (NTRS)
Rai, Man M.
2015-01-01
Design optimization methods that use the Reynolds-averaged Navier-Stokes equations with the associated turbulence and transition models, or other model-based forms of the governing equations, may result in aerodynamic designs with actual performance levels that are noticeably different from the expected values because of the complexity of modeling turbulence/transition accurately in certain flows. Flow phenomena such as wake-blade interaction and trailing edge vortex shedding in turbines and compressors (examples of such flows) may require a computational approach that is free of transition/turbulence models, such as direct numerical simulations (DNS), for the underlying physics to be computed accurately. Here we explore the possibility of utilizing DNS data in designing a turbine blade section. The ultimate objective is to substantially reduce differences between predicted performance metrics and those obtained in reality. The redesign of a typical low-pressure turbine blade section with the goal of reducing total pressure loss in the row is provided as an example. The basic ideas presented here are of course just as applicable elsewhere in aerodynamic shape optimization as long as the computational costs are not excessive.
Using optimal transport theory to estimate transition probabilities in metapopulation dynamics
Nichols, Jonathan M.; Spendelow, Jeffrey A.; Nichols, James
2017-01-01
This work considers the estimation of transition probabilities associated with populations moving among multiple spatial locations based on numbers of individuals at each location at two points in time. The problem is generally underdetermined as there exists an extremely large number of ways in which individuals can move from one set of locations to another. A unique solution therefore requires a constraint. The theory of optimal transport provides such a constraint in the form of a cost function, to be minimized in expectation over the space of possible transition matrices. We demonstrate the optimal transport approach on marked bird data and compare to the probabilities obtained via maximum likelihood estimation based on marked individuals. It is shown that by choosing the squared Euclidean distance as the cost, the estimated transition probabilities compare favorably to those obtained via maximum likelihood with marked individuals. Other implications of this cost are discussed, including the ability to accurately interpolate the population's spatial distribution at unobserved points in time and the more general relationship between the cost and minimum transport energy.
Kerswell, R R; Pringle, C C T; Willis, A P
2014-08-01
This article introduces and reviews recent work using a simple optimization technique for analysing the nonlinear stability of a state in a dynamical system. The technique can be used to identify the most efficient way to disturb a system such that it transits from one stable state to another. The key idea is introduced within the framework of a finite-dimensional set of ordinary differential equations (ODEs) and then illustrated for a very simple system of two ODEs which possesses bistability. Then the transition to turbulence problem in fluid mechanics is used to show how the technique can be formulated for a spatially-extended system described by a set of partial differential equations (the well-known Navier-Stokes equations). Within that context, the optimization technique bridges the gap between (linear) optimal perturbation theory and the (nonlinear) dynamical systems approach to fluid flows. The fact that the technique has now been recently shown to work in this very high dimensional setting augurs well for its utility in other physical systems.
Harlow, Siobán D; Mitchell, Ellen S; Crawford, Sybil; Nan, Bin; Little, Roderick; Taffe, John
2008-01-01
Criteria for staging the menopausal transition are not established. This article evaluates five bleeding criteria for defining early transition and provides empirically based guidance regarding optimal criteria. Prospective menstrual calendar data from four population-based cohorts: TREMIN, Melbourne Women's Midlife Health Project (MWMHP), Seattle Midlife Women's Health Study (SMWHS), and Study of Women's Health Across the Nation (SWAN) with annual serum FSH from MWMHP and SWAN. 735 TREMIN, 279 SMWHS, 216 MWMHP, and 2270 SWAN women aged 35-57 at baseline who maintained menstrual calendars. Age at and time to menopause for: standard deviation >6 and >8 days, persistent difference in consecutive segments >6 days, irregularity, and >or=45 day segment. Serum FSH concentration. Most women experienced each of the bleeding criteria. Except for a persistent >6 day difference that occurs earlier, the criteria occur at a similar age and at approximately the same age as late transition in a large proportion of women. FSH was associated with all proposed markers. The early transition may be best described by ovarian activity consistent with the persistent >6 day difference, but further study is needed, as other proposed criterion are consistent with later menstrual changes.
Harlow, Siobán D.; Mitchell, Ellen S.; Crawford, Sybil; Nan, Bin; Little, Roderick; Taffe, John
2008-01-01
Study objective Criteria for staging the menopausal transition are not established. This paper evaluates five bleeding criteria for defining early transition and provides empirically-based guidance regarding optimal criteria. Design/Setting Prospective menstrual calendar data from four population-based cohorts: TREMIN, Melbourne Women’s Midlife Health Project(MWMHP), Seattle Midlife Women’s Health Study(SMWHS), and Study of Women’s Health Across the Nation(SWAN) with annual serum follicle stimulating hormone (FSH) from MWMHP and SWAN. Participants 735 TREMIN, 279 SMWHS, 216 MWMHP, and 2270 SWAN women aged 35-57 at baseline who maintained menstrual calendars. Main outcome measure(s) Age at and time to menopause for: standard deviation >6 and >8 days, persistent difference in consecutive segments >6 days, irregularity, and >=45 day segment. Serum follicle stimulating hormone concentration. Results Most women experienced each of the bleeding criteria. Except for persistent >6 day difference which occurs earlier, the criteria occur at a similar age and at approximately the same age as late transition in a large proportion of women. FSH was associated with all proposed markers. Conclusions The early transition may be best described by ovarian activity consistent with the persistent >6 day difference, but further study is needed, as other proposed criterion are consistent with later menstrual changes. PMID:17681300
ERIC Educational Resources Information Center
Agnew, Jeanne L.; Choike, James R.
1987-01-01
Mathematical observations are made about some continuous curves, called transitions, encountered in well-known experiences. The transition parabola, the transition spiral, and the sidestep maneuver are presented. (MNS)
ERIC Educational Resources Information Center
Nathanson, Jeanne H., Ed.
1993-01-01
This theme issue on transitions for individuals with disabilities contains nine papers discussing transition programs and issues. "Transition Issues for the 1990s," by Michael J. Ward and William D. Halloran, discusses self-determination, school responsibility for transition, continued educational engagement of at-risk students, and service…
Explaining patterns in the school-to-work transition: An analysis using optimal matching.
Dorsett, Richard; Lucchino, Paolo
2014-12-01
This paper studies the school to work transition in the UK with the aim of achieving a richer understanding of individuals' trajectories in the five years after reaching school leaving age. By applying the technique of 'optimal matching' on data from 1991 to 2008, we group individuals' trajectories post-16, and identify a small number of distinct transition patterns. Our results suggest that while 9 out of 10 young people have generally positive experiences post-16, the remaining individuals exhibit a variety of histories that might warrant policy attention. We assess the extent to which characteristics at age 16 can predict which type of trajectory a young person will follow. Our analysis shows that, despite the apparent heterogeneity, virtually all at-risk trajectories are associated with a relatively small set of key 'risk factors': early pregnancy; low educational attainment and self-confidence; and disadvantaged family background. These characteristics are known to be strongly correlated across individuals and raise concerns about the degree of socio-economic polarisation in the transition from school to work.
Optimal Length of Conformational Transition Region in Protein Search for Targets on DNA.
Kochugaeva, Maria P; Berezhkovskii, Alexander M; Kolomeisky, Anatoly B
2017-09-07
The starting point of many fundamental biological processes is associated with protein molecules finding and recognizing specific sites on DNA. However, despite a large number of experimental and theoretical studies on protein search for targets on DNA, many molecular aspects of underlying mechanisms are still not well understood. Experiments show that proteins bound to DNA can switch between slow recognition and fast search conformations. However, from a theoretical point of view, such conformational transitions should slow down the protein search for specific sites on DNA, in contrast to available experimental observations. In addition, experiments indicate that the nucleotide composition near the target site is more symmetrically homogeneous, leading to stronger effective interactions between proteins and DNA at these locations. However, as has been shown theoretically, this should also make the search less efficient, which is not observed. We propose a possible resolution of these problems by suggesting that conformational transitions occur only within a segment around the target where stronger interactions between proteins and DNA are observed. Two theoretical methods, based on continuum and discrete-state stochastic calculations, are developed, allowing us to obtain a comprehensive dynamic description for the protein search process in this system. The existence of an optimal length of the conformational transition zone with the shortest mean search time is predicted.
Excited meson radiative transitions from lattice QCD using variationally optimized operators
NASA Astrophysics Data System (ADS)
Shultz, Christian J.; Dudek, Jozef J.; Edwards, Robert G.; Hadron Spectrum Collaboration
2015-06-01
We explore the use of "optimized" operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and nonzero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited-state mesons. The required two- and three-point correlation functions are efficiently computed using the distillation framework in which there is a factorization between quark propagation and operator construction, allowing for a large number of meson operators of definite momentum to be considered. We illustrate the method with a calculation using anisotopic lattices having three flavors of dynamical quark all tuned to the physical strange quark mass, considering form factors and transitions of pseudoscalar and vector meson excitations. The dependence on photon virtuality for a number of form factors and transitions is extracted, and some discussion of excited-state phenomenology is presented.
Excited meson radiative transitions from lattice QCD using variationally optimized operators
Shultz, Christian J.; Dudek, Jozef J.; Edwards, Robert G.
2015-06-02
We explore the use of 'optimized' operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and non-zero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited state mesons. The required two- and three-point correlation functions are efficiently computed using the distillation framework in which there is a factorization between quark propagation and operator construction, allowing for a large number of meson operators of definite momentum to be considered. We illustrate the method with a calculation using anisotopic lattices having three flavors of dynamical quark all tuned to the physical strange quark mass, considering form-factors and transitions of pseudoscalar and vector meson excitations. In conclusion, the dependence on photon virtuality for a number of form-factors and transitions is extracted and some discussion of excited-state phenomenology is presented.
May, Volkhard; Ambrosek, David; Oppel, Markus; Gonzalez, Leticia
2007-10-14
A systematic approach is presented to describe nonresonant multiphoton transitions, i.e., transitions between two electronic states without the presence of additional intermediate states resonant with the single-photon energy. The method is well suited to describe femtosecond spectroscopic experiments and, in particular, attempts to achieve laser pulse control of molecular dynamics. The obtained effective time-dependent Schroedinger equation includes effective couplings to the radiation field which combine powers of the field strength and effective transition dipole operators between the initial and final states. To arrive at time-local equations our derivation combines the well-known rotating wave approximation with the approximation of slowly varying amplitudes. Under these terms, the optimal control formalism can be readily extended to also account for nonresonant multiphoton events. Exemplary, nonresonant two- and three-photon processes, similar to those occurring in the recent femtosecond pulse-shaping experiments on CpMn(CO){sub 3}, are treated using related ab initio potential energy surfaces.
NASA Astrophysics Data System (ADS)
Espinoza, Néstor; Jordán, Andrés
2016-04-01
Very precise measurements of exoplanet transit light curves both from ground- and space-based observatories make it now possible to fit the limb-darkening coefficients in the transit-fitting procedure rather than fix them to theoretical values. This strategy has been shown to give better results, as fixing the coefficients to theoretical values can give rise to important systematic errors which directly impact the physical properties of the system derived from such light curves such as the planetary radius. However, studies of the effect of limb-darkening assumptions on the retrieved parameters have mostly focused on the widely used quadratic limb-darkening law, leaving out other proposed laws that are either simpler or better descriptions of model intensity profiles. In this work, we show that laws such as the logarithmic, square-root and three-parameter law do a better job that the quadratic and linear laws when deriving parameters from transit light curves, both in terms of bias and precision, for a wide range of situations. We therefore recommend to study which law to use on a case-by-case basis. We provide code to guide the decision of when to use each of these laws and select the optimal one in a mean-square error sense, which we note has a dependence on both stellar and transit parameters. Finally, we demonstrate that the so-called exponential law is non-physical as it typically produces negative intensities close to the limb and should therefore not be used.
ERIC Educational Resources Information Center
Field, David; And Others
1992-01-01
Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)
Optimal and robust control and estimation of transition, convection, and turbulence
NASA Astrophysics Data System (ADS)
Bewley, Thomas Robinson
The large increases in drag, cyclic structural loading, internal stresses, mixing, and heat transfer caused by turbulence in flows of engineering interest have motivated engineers to study turbulence and attempt to alter its effects. Recent advances in MEMS capabilities may soon make it possible to measure small-scale turbulent fluctuations of a flow and, subsequently, to apply coordinated small-scale forcing to the flow in order to achieve a desired large-scale effect. The present work attempts to develop techniques to derive the necessary control strategies for such control problems from first principles, leveraging our knowledge of the Navier-Stokes equation which governs these flows and our ability to simulate this equation accurately in simple configurations. By so doing, we bypass the ad hoc assumptions about the turbulence dynamics often used to determine such control strategies and develop several new tools for analysis of flow systems in the control setting. Approaching this difficult problem in steps of gradually increasing complexity, optimal and robust control theories are used in the present work to derive and demonstrate effective control and estimation strategies for three important model problems in fluid mechanics. The model problems considered are: (1)the application of linear optimal/robust control theory to the linear paths to transition in a plane channel, (2)the application of linear optimal/robust control theory to a low-order nonlinear chaotic convection problem, and (3)the application of optimal control theory in a DNS-based predictive control setting to the fully nonlinear problem of turbulence. In order to develop feedback algorithms for practical (disturbed) environments, it is recognized that a degree of robustness will be necessary in the control rules. In the final section of this work, a general framework for robust control for problems governed by the Navier-Stokes equation is established by mathematical analysis, laying the
Kröpelin, Tobias F; de Zeeuw, Dick; Remuzzi, Giuseppe; Bilous, Rudy; Parving, Hans-Henrik; Heerspink, Hiddo J L
2016-11-01
Albuminuria class transition (normo- to micro- to macroalbuminuria) is used as an intermediate end point to assess renoprotective drug efficacy. However, definitions of such class transition vary between trials. To determine the most optimal protocol, we evaluated the approaches used in four clinical trials testing the effect of renin-angiotensin-aldosterone system intervention on albuminuria class transition in patients with diabetes: the BENEDICT, the DIRECT, the ALTITUDE, and the IRMA-2 Trial. The definition of albuminuria class transition used in each trial differed from the definitions used in the other trials by the number (one, two, or three) of consecutively collected urine samples at each study visit, the time interval between study visits, the requirement of an additional visit to confirm the class transition, and the requirement of a percentage increase in albuminuria from baseline in addition to the class transition. In Cox regression analysis, neither increasing the number of urine samples collected at a single study visit nor differences in the other variables used to define albuminuria class transition altered the average drug effect. However, the SEM of the treatment effect increased (decreased precision) with stricter end point definitions, resulting in a loss of statistical significance. In conclusion, the optimal albuminuria transition end point for use in drug intervention trials can be determined with a single urine collection for albuminuria assessment per study visit. A confirmation of the end point or a requirement of a minimal percentage change in albuminuria from baseline seems unnecessary. Copyright © 2016 by the American Society of Nephrology.
Optimizing Transition Edge Sensors for High-Resolution X-ray Spectroscopy
Saab, Tarek; Bandler, Simon R.; Boyce, Kevin; Chervenak, James A.; Figueroa-Feliciano, Enectali; Iyomoto, Naoko; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E
2006-09-07
Transition Edge Sensors (TES) have found applications as astronomical detectors ranging from the microwave to the gamma ray energy bands. Each energy band, however, imposes a different set of requirements on the TES such as energy and timing resolution, focal plane coverage, and the mechanisms by which the signal is coupled to the detector. This paper focuses on the development of TESs optimized for the 0.1-10 keV energy range at the NASA Goddard Space Flight Center. Such detectors are suitable candidates for some of the upcoming X-ray observatories such as NeXT and Constellation-X. Ongoing efforts at producing, characterizing, and modeling such devices, as well as the latest results, are discussed.
NASA Astrophysics Data System (ADS)
Howe, Alex R.; Burrows, Adam; Deming, Drake
2017-01-01
We provide an example of an analysis to explore the optimization of observations of transiting hot Jupiters with the James Webb Space Telescope (JWST) to characterize their atmospheres based on a simple three-parameter forward model. We construct expansive forward model sets for 11 hot Jupiters, 10 of which are relatively well characterized, exploring a range of parameters such as equilibrium temperature and metallicity, as well as considering host stars over a wide range in brightness. We compute posterior distributions of our model parameters for each planet with all of the available JWST spectroscopic modes and several programs of combined observations and compute their effectiveness using the metric of estimated mutual information per degree of freedom. From these simulations, clear trends emerge that provide guidelines for designing a JWST observing program. We demonstrate that these guidelines apply over a wide range of planet parameters and target brightnesses for our simple forward model.
NASA Astrophysics Data System (ADS)
Bastidon, Noëmie; Horns, Dieter; Lindner, Axel
2016-07-01
The ALPS II experiment, Any Light Particle Search II at DESY in Hamburg, will look for sub-eV mass new fundamental bosons (e.g., axion-like particles, hidden photons, and other weakly interacting sub-eV particles) in the next years by means of a light-shining-through-wall setup. The ALPS II photosensor is a tungsten transition-edge sensor (W-TES) optimized for 1064 nm photons. This TES, operated at 80 mK, has already allowed single infrared photon detections as well as non-dispersive spectroscopy with very low background rates. The demonstrated quantum efficiency for such TES is up to 95 % (1064 nm) as has been already demonstrated by the US National Institute of Standards and Technology. A back-to-back measurement of the ALPS TES quantum efficiency using a calibrated charge-coupled device camera has lead to a first estimation of 30 %. Improvement methods are discussed.
Nonlinear optimal control of bypass transition in a boundary layer flow
NASA Astrophysics Data System (ADS)
Xiao, Dandan; Papadakis, George
2016-11-01
Bypass transition is observed in a flat-plate boundary-layer flow when high levels of free stream turbulence are present. This scenario is characterized by the formation of streamwise elongated streaks inside the boundary layer, their break down into turbulent spots and eventually fully turbulent flow. In the current work, we perform DNS simulations of control of bypass transition in a zero-pressure-gradient boundary layer. A non-linear optimal control algorithm is developed that employs the direct-adjoint approach to minimise a quadratic cost function based on the deviation from the Blasius velocity profile. Using the Lagrange variational approach, the distribution of the blowing/suction control velocity is found by solving iteratively the non-linear Navier-Stokes and its adjoint equations in a forward/backward loop. The optimisation is performed over a finite time horizon during which the Lagrange functional is to be minimised. Large values of optimisation horizon result in instability of the adjoint equations. The results show that the controller is able to reduce the turbulent kinetic energy of the flow in the region where the objective function is defined and the velocity profile is seen to approach the Blasius solution. Significant drag reduction is also achieved.
Shen, Bo-Ran; Zhu, Cheng-Hua; Yao, Zhen; Cui, Li-Li; Zhang, Jian-Jun; Yang, Cheng-Wei; He, Zheng-Hui; Peng, Xin-Xiang
2017-01-01
Various chloroplast transit peptides (CTP) have been used to successfully target some foreign proteins into chloroplasts, but for other proteins these same CTPs have reduced localization efficiencies or fail completely. The underlying cause of the failures remains an open question, and more effective CTPs are needed. In this study, we initially observed that two E.coli enzymes, EcTSR and EcGCL, failed to be targeted into rice chloroplasts by the commonly-used rice rbcS transit peptide (rCTP) and were subsequently degraded. Further analyses revealed that the N-terminal unfolded region of cargo proteins is critical for their localization capability, and that a length of about 20 amino acids is required to attain the maximum localization efficiency. We considered that the unfolded region may alleviate the steric hindrance produced by the cargo protein, by functioning as a spacer to which cytosolic translocators can bind. Based on this inference, an optimized CTP, named RC2, was constructed. Analyses showed that RC2 can more effectively target diverse proteins, including EcTSR and EcGCL, into rice chloroplasts. Collectively, our results provide further insight into the mechanism of CTP-mediated chloroplastic localization, and more importantly, RC2 can be widely applied in future chloroplastic metabolic engineering, particularly for crop plants. PMID:28397859
Optimized 3D stitching algorithm for whole body SPECT based on transition error minimization (TEM)
NASA Astrophysics Data System (ADS)
Cao, Xinhua; Xu, Xiaoyin; Voss, Stephan
2017-02-01
Standard Single Photon Emission Computed Tomography (SPECT) has a limited field of view (FOV) and cannot provide a 3D image of an entire long whole body SPECT. To produce a 3D whole body SPECT image, two to five overlapped SPECT FOVs from head to foot are acquired and assembled using image stitching. Most commercial software from medical imaging manufacturers applies a direct mid-slice stitching method to avoid blurring or ghosting from 3D image blending. Due to intensity changes across the middle slice of overlapped images, direct mid-slice stitching often produces visible seams in the coronal and sagittal views and maximal intensity projection (MIP). In this study, we proposed an optimized algorithm to reduce the visibility of stitching edges. The new algorithm computed, based on transition error minimization (TEM), a 3D stitching interface between two overlapped 3D SPECT images. To test the suggested algorithm, four studies of 2-FOV whole body SPECT were used and included two different reconstruction methods (filtered back projection (FBP) and ordered subset expectation maximization (OSEM)) as well as two different radiopharmaceuticals (Tc-99m MDP for bone metastases and I-131 MIBG for neuroblastoma tumors). Relative transition errors of stitched whole body SPECT using mid-slice stitching and the TEM-based algorithm were measured for objective evaluation. Preliminary experiments showed that the new algorithm reduced the visibility of the stitching interface in the coronal, sagittal, and MIP views. Average relative transition errors were reduced from 56.7% of mid-slice stitching to 11.7% of TEM-based stitching. The proposed algorithm also avoids blurring artifacts by preserving the noise properties of the original SPECT images.
Optimal Body Temperature in Transitional ELBW Infants Using Heart Rate and Temperature as Indicators
Knobel, Robin B.; Holditch-Davis, Diane; Schwartz, Todd A.
2013-01-01
Extremely low birth weight (ELBW) infants are vulnerable to cold stress after birth. Therefore, caregivers need to control body temperature optimally to minimize energy expenditure. Objective We explored body temperature in relationship to heart rate in ELBW infants during their first 12 hours to help identify the ideal set point for incubator control of body temperature. Design Within subject, multiple-case design. Setting A tertiary NICU in North Carolina. Participants 10 infants, born less than 29 weeks gestation and weighing 400-1000 grams. Methods Heart rate and abdominal body temperature were measured at 1-minute intervals for 12 hours. Heart rates were considered normal if they were between the 25th and 75th percentile for each infant. Results Abdominal temperatures were low throughout the 12-hour study period (mean 35.17° C-36.68° C). Seven of ten infants had significant correlations between abdominal temperature and heart rate. Heart rates above the 75th percentile were associated with low and high abdominal temperatures; heart rates less than the 25th percentile were associated with very low abdominal temperatures. The extent to which abdominal temperature was abnormally low was related the extent to which the heart rate trended away from normal in six of the ten infants. Optimal temperature control point that maximized normal heart rate observations for each infant was between 36.8° C and 37° C. Conclusions Hypothermia was associated with abnormal heart rates in transitional ELBW infants. We suggest nurses set incubator servo between 36.8° C and 36.9° C to optimally control body temperature for ELBW infants. PMID:20409098
Combinatorial optimization using dynamical phase transitions in driven-dissipative systems.
Leleu, Timothée; Yamamoto, Yoshihisa; Utsunomiya, Shoko; Aihara, Kazuyuki
2017-02-01
The dynamics of driven-dissipative systems is shown to be well-fitted for achieving efficient combinatorial optimization. The proposed method can be applied to solve any combinatorial optimization problem that is equivalent to minimizing an Ising Hamiltonian. Moreover, the dynamics considered can be implemented using various physical systems as it is based on generic dynamics-the normal form of the supercritical pitchfork bifurcation. The computational principle of the proposed method relies on an hybrid analog-digital representation of the binary Ising spins by considering the gradient descent of a Lyapunov function that is the sum of an analog Ising Hamiltonian and archetypal single or double-well potentials. By gradually changing the shape of the latter potentials from a single to double well shape, it can be shown that the first nonzero steady states to become stable are associated with global minima of the Ising Hamiltonian, under the approximation that all analog spins have the same amplitude. In the more general case, the heterogeneity in amplitude between analog spins induces the stabilization of local minima, which reduces the quality of solutions to combinatorial optimization problems. However, we show that the heterogeneity in amplitude can be reduced by setting the parameters of the driving signal near a regime, called the dynamic phase transition, where the analog spins' DC components map more accurately the global minima of the Ising Hamiltonian which, in turn, increases the quality of solutions found. Last, we discuss the possibility of a physical implementation of the proposed method using networks of degenerate optical parametric oscillators.
Combinatorial optimization using dynamical phase transitions in driven-dissipative systems
NASA Astrophysics Data System (ADS)
Leleu, Timothée; Yamamoto, Yoshihisa; Utsunomiya, Shoko; Aihara, Kazuyuki
2017-02-01
The dynamics of driven-dissipative systems is shown to be well-fitted for achieving efficient combinatorial optimization. The proposed method can be applied to solve any combinatorial optimization problem that is equivalent to minimizing an Ising Hamiltonian. Moreover, the dynamics considered can be implemented using various physical systems as it is based on generic dynamics—the normal form of the supercritical pitchfork bifurcation. The computational principle of the proposed method relies on an hybrid analog-digital representation of the binary Ising spins by considering the gradient descent of a Lyapunov function that is the sum of an analog Ising Hamiltonian and archetypal single or double-well potentials. By gradually changing the shape of the latter potentials from a single to double well shape, it can be shown that the first nonzero steady states to become stable are associated with global minima of the Ising Hamiltonian, under the approximation that all analog spins have the same amplitude. In the more general case, the heterogeneity in amplitude between analog spins induces the stabilization of local minima, which reduces the quality of solutions to combinatorial optimization problems. However, we show that the heterogeneity in amplitude can be reduced by setting the parameters of the driving signal near a regime, called the dynamic phase transition, where the analog spins' DC components map more accurately the global minima of the Ising Hamiltonian which, in turn, increases the quality of solutions found. Last, we discuss the possibility of a physical implementation of the proposed method using networks of degenerate optical parametric oscillators.
NASA Astrophysics Data System (ADS)
Huhn, Oliver; Hauck, Judith; Hoppema, Mario; Rhein, Monika; Roether, Wolfgang
2010-05-01
We use a 20 year time series of chlorofluorocarbon (CFC) observations along the Prime Meridian to determine the temporal evolution of anthropogenic carbon (Cant) in the two deep boundary currents which enter the Weddell Basin in the south and leave it in the north. The Cant is inferred from transit time distributions (TTDs), with parameters (mean transit time and dispersion) adjusted to the observed mean CFC histories in these recently ventilated deep boundary currents. We optimize that "classic" TTD approach by accounting for water exchange of the boundary currents with an old but not CFC and Cant free interior reservoir. This reservoir in turn, is replenished by the boundary currents, which we parameterize as first order mixing. Furthermore, we account for the time-dependence of the CFC and Cant source water saturation. A conceptual model of an ideal saturated mixed layer and exchange with adjacent water is adjusted to observed CFC saturations in the source regions. The time-dependence for the CFC saturation appears to be much weaker than for Cant. We find a mean transit time of 14 years and an advection/dispersion ratio of 5 for the deep southern boundary current. For the northern boundary current we find a mean transit time of 8 years and a much advection/dispersion ratio of 140. The fractions directly supplied by the boundary currents are in both cases in the order of 10%, while 90% are admixed from the interior reservoirs, which are replenished with a renewal time of about 14 years. We determine Cant ~ 11 umol/kg (reference year 2006) in the deep water entering the Weddell Sea in the south (~2.1 Sv), and 12 umol/kg for the deep water leaving the Weddell Sea in the north (~2.7 Sv). These Cant estimates are, however, upper limits, considering that the Cant source water saturation is likely to be lower than that for the CFCs. Comparison with Cant intrusion estimates based on extended multiple linear regression (using potential temperature, salinity, oxygen, and
ERIC Educational Resources Information Center
Thompson, Sandy, Ed.; And Others
1990-01-01
This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…
NASA Astrophysics Data System (ADS)
Markowski, Konrad; Jedrzejewski, Kazimierz; Osuch, Tomasz
2016-09-01
This article presents implementation of the Simulated Annealing (SA) algorithm for tapered fiber Bragg gratings (TFBGs) design. Particularly, together with well-known Coupled Mode Theory (CMT) and Transfer Matrix Method (TMM) the algorithm optimizes the group delay response of TFBG, by simultaneous shaping of both apodization function and tapered fiber transition profile. Prior to the optimization process, numerical model for TFBG design has been validated. Preliminary results reveal great potential of the SA-based approach and with proper definition of the design criteria may be even applied for optimization of the spectral properties of TFBGs.
ERIC Educational Resources Information Center
Morton, Stephen; Mergler, Amanda; Boman, Peter
2014-01-01
Students making the transition from high school to university often encounter many stressors and new experiences. Many students adjust successfully to university; however, some students do not, often resulting in attrition from the university and mental health issues. The primary aim of the current study was to examine the effects that optimism,…
ERIC Educational Resources Information Center
Morton, Stephen; Mergler, Amanda; Boman, Peter
2014-01-01
Students making the transition from high school to university often encounter many stressors and new experiences. Many students adjust successfully to university; however, some students do not, often resulting in attrition from the university and mental health issues. The primary aim of the current study was to examine the effects that optimism,…
Study of the Bus Dynamic Coscheduling Optimization Method under Urban Rail Transit Line Emergency
Yan, Xuedong; Wang, Jiaxi; Chen, Shasha
2014-01-01
As one of the most important urban commuter transportation modes, urban rail transit (URT) has been acting as a key solution for supporting mobility needs in high-density urban areas. However, in recent years, high frequency of unexpected events has caused serious service disruptions in URT system, greatly harming passenger safety and resulting in severe traffic delays. Therefore, there is an urgent need to study emergency evacuation problem in URT. In this paper, a method of bus dynamic coscheduling is proposed and two models are built based on different evacuation destinations including URT stations and surrounding bus parking spots. A dynamic coscheduling scheme for buses can be obtained by the models. In the model solution process, a new concept—the equivalent parking spot—is proposed to transform the nonlinear model into an integer linear programming (ILP) problem. A case study is conducted to verify the feasibility of models. Also, sensitivity analysis of two vital factors is carried out to analyze their effects on the total evacuation time. The results reveal that the designed capacity of buses has a negative influence on the total evacuation time, while an increase in the number of passengers has a positive effect. Finally, some significant optimizing strategies are proposed. PMID:25530750
Study of the bus dynamic coscheduling optimization method under urban rail transit line emergency.
Wang, Yun; Yan, Xuedong; Zhou, Yu; Wang, Jiaxi; Chen, Shasha
2014-01-01
As one of the most important urban commuter transportation modes, urban rail transit (URT) has been acting as a key solution for supporting mobility needs in high-density urban areas. However, in recent years, high frequency of unexpected events has caused serious service disruptions in URT system, greatly harming passenger safety and resulting in severe traffic delays. Therefore, there is an urgent need to study emergency evacuation problem in URT. In this paper, a method of bus dynamic coscheduling is proposed and two models are built based on different evacuation destinations including URT stations and surrounding bus parking spots. A dynamic coscheduling scheme for buses can be obtained by the models. In the model solution process, a new concept-the equivalent parking spot-is proposed to transform the nonlinear model into an integer linear programming (ILP) problem. A case study is conducted to verify the feasibility of models. Also, sensitivity analysis of two vital factors is carried out to analyze their effects on the total evacuation time. The results reveal that the designed capacity of buses has a negative influence on the total evacuation time, while an increase in the number of passengers has a positive effect. Finally, some significant optimizing strategies are proposed.
Optimizing Transition-Edge Sensor Design for High Count-Rate Applications
Smith, Stephen J.; Adams, Joe S.; Bandler, Simon R.; Brekosky, Regis P.; Brown, Ari-D.; Chervenak, James A.; Eckart, Megan E.; Kelley, Richard L.; Kilbourne, Caroline A.; Scott Porter, F.; Finkbeiner, Fred M.; Sadleir, John E.
2009-12-16
We are developing transition-edge sensor (TES) X-ray detectors optimized for high count-rate applications. These devices are fabricated on thick (300 {mu}m) Si substrates, resulting in a 20 times increase in thermal conductance to the heat sink compared to our conventional membrane isolated TES's. Operating a TES with higher heat sink conductance requires 4.5 times more bias current. This results in a 2.7 times increase in {beta}, the logarithmic derivative of resistance with respect to current. Noise measurements show a lower limit on the TES excess noise scales as (2{beta}){sup 1/2}, consistent with the near-equilibrium, non-linear expansion of the Ohmic Johnson noise. This is consistent with our membrane devices though the increased {beta} means the theoretical best attainable resolution is degraded by 25-35%. We have tested devices with different contact geometries between the absorber, and the TES and substrate. This allows us to investigate the loss of athermal phonons to the substrate, which can degrade the resolution. Results show a correlation between the stem contact area and a low-energy tail in the spectral response at 5.9 keV due to the athermal phonon loss. In several devices tested we demonstrate a resolution of 4.1-5.6 eV, coupled with detector time constants as fast as 44 {mu}s, representing an increase in detector response by 7 times compared to the membrane devices.
Streamlining the Design-to-Build Transition with Build-Optimization Software Tools.
Oberortner, Ernst; Cheng, Jan-Fang; Hillson, Nathan J; Deutsch, Samuel
2017-03-17
Scaling-up capabilities for the design, build, and test of synthetic biology constructs holds great promise for the development of new applications in fuels, chemical production, or cellular-behavior engineering. Construct design is an essential component in this process; however, not every designed DNA sequence can be readily manufactured, even using state-of-the-art DNA synthesis methods. Current biological computer-aided design and manufacture tools (bioCAD/CAM) do not adequately consider the limitations of DNA synthesis technologies when generating their outputs. Designed sequences that violate DNA synthesis constraints may require substantial sequence redesign or lead to price-premiums and temporal delays, which adversely impact the efficiency of the DNA manufacturing process. We have developed a suite of build-optimization software tools (BOOST) to streamline the design-build transition in synthetic biology engineering workflows. BOOST incorporates knowledge of DNA synthesis success determinants into the design process to output ready-to-build sequences, preempting the need for sequence redesign. The BOOST web application is available at https://boost.jgi.doe.gov and its Application Program Interfaces (API) enable integration into automated, customized DNA design processes. The herein presented results highlight the effectiveness of BOOST in reducing DNA synthesis costs and timelines.
Alghanem, Bandar; Nikitin, Frédéric; Stricker, Thomas; Duchoslav, Eva; Luban, Jeremy; Strambio-De-Castillia, Caterina; Muller, Markus; Lisacek, Frédérique; Varesio, Emmanuel; Hopfgartner, Gérard
2017-05-15
In peptide quantification by liquid chromatography/mass spectrometry (LC/MS), the optimization of multiple reaction monitoring (MRM) parameters is essential for sensitive detection. We have compared different approaches to build MRM assays, based either on flow injection analysis (FIA) of isotopically labelled peptides, or on the knowledge and the prediction of the best settings for MRM transitions and collision energies (CE). In this context, we introduce MRMOptimizer, an open-source software tool that processes spectra and assists the user in selecting transitions in the FIA workflow. MS/MS spectral libraries with CE voltages from 10 to 70 V are automatically acquired in FIA mode for isotopically labelled peptides. Then MRMOptimizer determines the optimal MRM settings for each peptide. To assess the quantitative performance of our approach, 155 peptides, representing 84 proteins, were analysed by LC/MRM-MS and the peak areas were compared between: (A) the MRMOptimizer-based workflow, (B1) the SRMAtlas transitions set used 'as-is'; (B2) the same SRMAtlas set with CE parameters optimized by Skyline. 51% of the three most intense transitions per peptide were shown to be common to both A and B1/B2 methods, and displayed similar sensitivity and peak area distributions. The peak areas obtained with MRMOptimizer for transitions sharing either the precursor ion charge state or the fragment ions with the SRMAtlas set at unique transitions were increased 1.8- to 2.3-fold. The gain in sensitivity using MRMOptimizer for transitions with different precursor ion charge state and fragment ions (8% of the total), reaches a ~ 11-fold increase. Isotopically labelled peptides can be used to optimize MRM transitions more efficiently in FIA than by searching databases. The MRMOptimizer software is MS independent and enables the post-acquisition selection of MRM parameters. Coefficients of variation for optimal CE values are lower than those obtained with the SRMAtlas approach (B2
Near-optimal energy transitions for energy-state trajectories of hypersonic aircraft
NASA Technical Reports Server (NTRS)
Ardema, M. D.; Bowles, J. V.; Terjesen, E. J.; Whittaker, T.
1992-01-01
A problem of the instantaneous energy transition that occurs in energy-state approximation is considered. The transitions are modeled as a sequence of two load-factor bounded paths (either climb-dive or dive-climb). The boundary-layer equations associated with the energy-state dynamic model are analyzed to determine the precise location of the transition.
Cadieu, F.J.
1990-12-31
This report reviews work on the optimization of film synthesized rare earth transition metal permanent magnet systems. Topics include: high coercivity in Sm-Fe-Ti-V, Sm-Fe-V, and two element systems; ThMn{sub 12} type pseudobinary SmFe{sub 12 {minus} X}T{sub X}; and sputter process control for the synthesis of precisely textured RE-TM magnetic films. (JL)
Burke, Robert E.; Malone, Daniel; Ridgeway, Kyle J.; McManus, Beth M.; Stevens-Lapsley, Jennifer E.
2016-01-01
Hospital readmissions in older adult populations are an emerging quality indicator for acute care hospitals. Recent evidence has linked functional decline during and after hospitalization with an elevated risk of hospital readmission. However, models of care that have been developed to reduce hospital readmission rates do not adequately address functional deficits. Physical therapists, as experts in optimizing physical function, have a strong opportunity to contribute meaningfully to care transition models and demonstrate the value of physical therapy interventions in reducing readmissions. Thus, the purposes of this perspective article are: (1) to describe the need for physical therapist input during care transitions for older adults and (2) to outline strategies for expanding physical therapy participation in care transitions for older adults, with an overall goal of reducing avoidable 30-day hospital readmissions. PMID:26939601
Yu, Yuqi; Wang, Jinan; Shao, Qiang E-mail: Jiye.Shi@ucb.com Zhu, Weiliang E-mail: Jiye.Shi@ucb.com; Shi, Jiye E-mail: Jiye.Shi@ucb.com
2015-03-28
The application of temperature replica exchange molecular dynamics (REMD) simulation on protein motion is limited by its huge requirement of computational resource, particularly when explicit solvent model is implemented. In the previous study, we developed a velocity-scaling optimized hybrid explicit/implicit solvent REMD method with the hope to reduce the temperature (replica) number on the premise of maintaining high sampling efficiency. In this study, we utilized this method to characterize and energetically identify the conformational transition pathway of a protein model, the N-terminal domain of calmodulin. In comparison to the standard explicit solvent REMD simulation, the hybrid REMD is much less computationally expensive but, meanwhile, gives accurate evaluation of the structural and thermodynamic properties of the conformational transition which are in well agreement with the standard REMD simulation. Therefore, the hybrid REMD could highly increase the computational efficiency and thus expand the application of REMD simulation to larger-size protein systems.
Yu, Yuqi; Wang, Jinan; Shao, Qiang; Shi, Jiye; Zhu, Weiliang
2015-03-28
The application of temperature replica exchange molecular dynamics (REMD) simulation on protein motion is limited by its huge requirement of computational resource, particularly when explicit solvent model is implemented. In the previous study, we developed a velocity-scaling optimized hybrid explicit/implicit solvent REMD method with the hope to reduce the temperature (replica) number on the premise of maintaining high sampling efficiency. In this study, we utilized this method to characterize and energetically identify the conformational transition pathway of a protein model, the N-terminal domain of calmodulin. In comparison to the standard explicit solvent REMD simulation, the hybrid REMD is much less computationally expensive but, meanwhile, gives accurate evaluation of the structural and thermodynamic properties of the conformational transition which are in well agreement with the standard REMD simulation. Therefore, the hybrid REMD could highly increase the computational efficiency and thus expand the application of REMD simulation to larger-size protein systems.
Structural and magnetic phase transitions near optimal superconductivity in BaFe2(As1-xPx)2
Hu, Ding; Lu, Xingye; Zhang, Wenliang; ...
2015-04-17
In this study, we use nuclear magnetic resonance (NMR), high-resolution x-ray and neutron scattering to study structural and magnetic phase transitions in phosphorus-doped BaFe2(As1-xPx)2. Thus, previous transport, NMR, specific heat, and magnetic penetration depth measurements have provided compelling evidence for the presence of a quantum critical point (QCP) near optimal superconductivity at x = 0.3. However, we show that the tetragonal-to-orthorhombic structural (Ts) and paramagnetic to antiferromagnetic (AF, TN) transitions in BaFe2(As1-xPx)2 are always coupled and approach to TN ≈ Ts ≥ Tc (≈ 29 K) for x = 0.29 before vanishing abruptly for x ≥ 0.3. These results suggestmore » that AF order in BaFe2(As1-xPx)2 disappears in a weakly first order fashion near optimal superconductivity, much like the electron-doped iron pnictides with an avoided QCP.« less
NASA Astrophysics Data System (ADS)
Wang, Jiangliu; Li, Wei
2015-10-01
In this paper, we consider a defense-intrusion interaction, in which an intruder is attracted by a protected stationary target but repulsed by a defender; while the defender tries to move towards an appropriate interception position (IP) between the intruder and the target in order to intercept the intruder and expel the intruder away from the target as maximum as possible. Intuitionally, to keep the intruder further away, one may wonder that: is it a better strategy for the defender trying to approach the intruder as near as possible? Unexpectedly and interestingly enough, this is not always the case. We first introduce the flexibility for IP selection, then investigate the system dynamics and the stable motion patterns, and characterize the phase-transition surface for the motion patterns. We show that, the phase-transition surface just defines the optimal interception strategy of the defender for IP selection; and from the perspective of mobility of agents, the optimal strategy just depends on relative mobility of the two agents.
Gerrits, Thomas; Calkins, Brice; Tomlin, Nathan; Lita, Adriana E; Migdall, Alan; Mirin, Richard; Nam, Sae Woo
2012-10-08
Typically, transition edge sensors resolve photon number of up to 10 or 20 photons, depending on the wavelength and TES design. We extend that dynamic range up to 1000 photons, while maintaining sub-shot noise detection process uncertainty of the number of detected photons and beyond that show a monotonic response up to ≈ 6 · 10(6) photons in a single light pulse. This mode of operation, which heats the sensor far beyond its transition edge into the normal conductive regime, offers a technique for connecting single-photon-counting measurements to radiant-power measurements at picowatt levels. Connecting these two usually incompatible operating regimes in a single detector offers significant potential for directly tying photon counting measurements to conventional cryogenic radiometric standards. In addition, our measurements highlight the advantages of a photon-number state source over a coherent pulse source as a tool for characterizing such a detector.
Length optimization of an S-shaped transition between offset optical waveguides.
Marcuse, D
1978-03-01
We derive expressions for the radiation loss of an S-shaped waveguide transition used to connect two straight integrated optics waveguides that are offset with respect to each other. It is assumed that the diffused integrated optics waveguides are produced with the help of an electron beam machine that allows beam positioning in the y direction only in discrete steps. We thus must consider staircase approximations to the desired smooth S-shaped curves. A waveguide whose axis consists of a staircase suffers radiation losses due to the quasi-periodic deformation of its axis. A second loss contribution comes from the S-shape of the waveguide axis. The sum of these loss contributions assumes a minimum that defines the optimum length of the transition waveguide.
Optimization of film synthesized rare earth transition metal permanent magnet systems
Cadieu, F.J.
1992-01-01
Progress is reported in three areas: high coercivity Sm-Fe-Ti-V, Sm-Fe-Zr, and two element Sm-Fe Sm{sub 5}(Fe,T){sub 17} type crystalline phases; ThMn{sub 12} type pseudobinary SmFe{sub 12-x}T{sub x}(0{le}{times}{le}1.5); and sputter process control for the synthesis of precisely textured rare earth-transition metal magnetic films. (DLC)
Campos, Daniel; Méndez, Vicenç
2015-12-01
Recent works have explored the properties of Lévy flights with resetting in one-dimensional domains and have reported the existence of phase transitions in the phase space of parameters which minimizes the mean first passage time (MFPT) through the origin [L. Kusmierz et al., Phys. Rev. Lett. 113, 220602 (2014)]. Here, we show how actually an interesting dynamics, including also phase transitions for the minimization of the MFPT, can also be obtained without invoking the use of Lévy statistics but for the simpler case of random walks with exponentially distributed flights of constant speed. We explore this dynamics both in the case of finite and infinite domains, and for different implementations of the resetting mechanism to show that different ways to introduce resetting consistently lead to a quite similar dynamics. The use of exponential flights has the strong advantage that exact solutions can be obtained easily for the MFPT through the origin, so a complete analytical characterization of the system dynamics can be provided. Furthermore, we discuss in detail how the phase transitions observed in random walks with resetting are closely related to several ideas recurrently used in the field of random search theory, in particular, to other mechanisms proposed to understand random search in space as mortal random walks or multiscale random walks. As a whole, we corroborate that one of the essential ingredients behind MFPT minimization lies in the combination of multiple movement scales (regardless of their specific origin).
Smart, Eric; Aulakh, Adeeta; McDougall, Carolyn; Rigby, Patty; King, Gillian
2017-10-01
Identify strategies youth perceive will optimize their engagement in goal pursuit in life skills and transition programs using an engagement framework involving affective, cognitive, and behavioral components. A qualitative descriptive design was used. Two semi-structured interviews were conducted with seven youth. The first was informed by a prior observation session, and the second occurred after the program ended and explored youths' perceptions of whether and how their engagement changed. Data were analyzed using thematic analysis. The analysis generated eight strategies youth considered effective. These were categorized under the three components of engagement. Affective strategies: (1) building a relationship on familiarity and reciprocity; and (2) guiding the program using youths' preferences and strengths. Cognitive strategies: (3) assisting youth to envision meaningful change; (4) utilizing youths' learning styles; and (5) promoting awareness of goal progress. Behavioral strategies: (6) ensuring youth access to a resource network; (7) providing youth multiple decision opportunities; and (8) enabling youth to showcase capabilities. Service providers together with youth are encouraged to consider the role of context and self-determination needs in order to optimize youth engagement in goal pursuit. Systematic approaches to studying engagement are necessary to learn how to maximize rehabilitation potential. Implications for Rehabilitation Service providers are encouraged to be aware of the nature of engagement strategies identified by youth. Comprehensive frameworks of engagement are essential to generate knowledge on the range of strategies service providers can use to engage clients in rehabilitation services. Strategies perceived by youth to optimize their engagement in goal pursuit in life skills and transition programs have subtle yet significant differences with strategies used in other rehabilitation settings like mental health and adult healthcare
NASA Technical Reports Server (NTRS)
Burcham, Frank W., Jr.; Gilyard, Glenn B.; Myers, Lawrence P.
1990-01-01
Integration of propulsion and flight control systems and their optimization offers significant performance improvements. Research programs were conducted which have developed new propulsion and flight control integration concepts, implemented designs on high-performance airplanes, demonstrated these designs in flight, and measured the performance improvements. These programs, first on the YF-12 airplane, and later on the F-15, demonstrated increased thrust, reduced fuel consumption, increased engine life, and improved airplane performance; with improvements in the 5 to 10 percent range achieved with integration and with no changes to hardware. The design, software and hardware developments, and testing requirements were shown to be practical.
Optimizing the superconducting transition temperature and upper critical field of Sn1-xInxTe
NASA Astrophysics Data System (ADS)
Zhong, R. D.; Schneeloch, J. A.; Shi, X. Y.; Xu, Z. J.; Zhang, C.; Tranquada, J. M.; Li, Q.; Gu, G. D.
2013-07-01
Sn1-xInxTe is a possible candidate for topological superconductivity. Previous work has shown that substitution of In for Sn in the topological crystalline insulator SnTe results in superconductivity, with the transition temperature, Tc, growing with In concentration. We have performed a systematic investigation of Sn1-xInxTe for a broad range of x, synthesizing single crystals (by a modified floating-zone method) as well as polycrystalline samples. The samples have been characterized by x-ray diffraction, resistivity, and magnetization. For the single crystals, the maximum Tc is obtained at x=0.45 with a value of 4.5 K, as determined by the onset of diamagnetism.
A self-contained, automated methodology for optimal flow control validated for transition delay
NASA Technical Reports Server (NTRS)
Joslin, Ronald D.; Gunzburger, Max D.; Nicolaides, R. A.; Erlebacher, Gordon; Hussaini, M. Yousuff
1995-01-01
This paper describes a self-contained, automated methodology for flow control along with a validation of the methodology for the problem of boundary layer instability suppression. The objective of control is to match the stress vector along a portion of the boundary to a given vector; instability suppression is achieved by choosing the given vector to be that of a steady base flow, e.g., Blasius boundary layer. Control is effected through the injection or suction of fluid through a single orifice on the boundary. The present approach couples the time-dependent Navier-Stokes system with an adjoint Navier-Stokes system and optimality conditions from which optimal states, i.e., unsteady flow fields, and control, e.g., actuators, may be determined. The results demonstrate that instability suppression can be achieved without any a priori knowledge of the disturbance, which is significant because other control techniques have required some knowledge of the flow unsteadiness such as frequencies, instability type, etc.
Design and Optimization of Multi-Pixel Transition-Edge Sensors for X-Ray Astronomy Applications
NASA Technical Reports Server (NTRS)
Smith, Stephen J.; Adams, Joseph S.; Bandler, Simon R.; Chervenak, James A.; Datesman, Aaron Michael; Eckart, Megan E.; Ewin, Audrey J.; Finkbeiner, Fred M.; Kelley, Richard L.; Kilbourne, Caroline A.;
2017-01-01
Multi-pixel transition-edge sensors (TESs), commonly referred to as 'hydras', are a type of position sensitive micro-calorimeter that enables very large format arrays to be designed without commensurate increase in the number of readout channels and associated wiring. In the hydra design, a single TES is coupled to discrete absorbers via varied thermal links. The links act as low pass thermal filters that are tuned to give a different characteristic pulse shape for x-ray photons absorbed in each of the hydra sub pixels. In this contribution we report on the experimental results from hydras consisting of up to 20 pixels per TES. We discuss the design trade-offs between energy resolution, position discrimination and number of pixels and investigate future design optimizations specifically targeted at meeting the readout technology considered for Lynx.
Vortex phase transition and anisotropy behavior of optimized (Li1-x Fe x OH)FeSe single crystals
NASA Astrophysics Data System (ADS)
Yi, Xiaolei; Wang, Chunlei; Tang, Qingbin; Peng, Tao; Qiu, Yang; Xu, Junqi; Sun, Haibin; Luo, Yongsong; Yu, Benhai
2016-10-01
(Li1-x Fe x OH)FeSe single crystals have been successfully synthesized by a hydrothermal ion-exchange technique. We have carried out systematic research on the influence of the concentration of selenourea (c m) on the superconducting properties of (Li1-x Fe x OH)FeSe single crystals. The optimized specimens possess an onset superconducting transition temperature T c of up to 42 K obtained at c m = 0.8 mol l-1, and the corresponding residual resistivity ratio (RRR = ρ (300 K)/ρ (T c)) is estimated to be 11. The vortex liquid-to-glass phase transition has been discussed based on the collective pinning model. The large distance between the H g and H c2 lines, as well as the much narrower region of the pinned vortex-liquid phase, indicate a weak vortex-pinning ability in (Li1-x Fe x OH)FeSe single crystals. The big out-plane anisotropy behavior versus temperature has been explored according to the anisotropic Ginzburg-Landau theory, and the anisotropy factor Γ displays linear behavior towards temperature similar to that of SmFeAsO1-x F x superconductors.
Gawroński, Piotr; Górecka, Magdalena; Bederska, Magdalena; Rusaczonek, Anna; Ślesak, Ireneusz; Kruk, Jerzy; Karpiński, Stanisław
2013-01-01
Isochorismate synthase 1 (ICS1) is a crucial enzyme in the salicylic acid (SA) synthesis pathway, and thus it is important for immune defences. The ics1 mutant is used in experiments on plant–pathogen interactions, and ICS1 is required for the appropriate hypersensitive disease defence response. However, ICS1 also takes part in the synthesis of phylloquinone, which is incorporated into photosystem I and is an important component of photosynthetic electron transport in plants. Therefore, photosynthetic and molecular analysis of the ics1 mutant in comparison with wild-type and SA-degrading transgenic NahG Arabidopsis thaliana plants was performed. Photosynthetic parameters in the ics1 mutant, when compared with the wild type, were changed in a manner observed previously for state transition-impaired plants (STN7 kinase recessive mutant, stn7). In contrast to stn7, deregulation of the redox status of the plastoquinone pool (measured as 1–q p) in ics1 showed significant variation depending on the leaf age. SA-degrading transgenic NahG plants targeted to the cytoplasm or chloroplasts displayed normal (wild-type-like) state transition. However, ics1 plants treated with a phylloquinone precursor displayed symptoms of phenotypic reversion towards the wild type. ics1 also showed altered thylakoid structure with an increased number of stacked thylakoids per granum which indicates the role of ICS1 in regulation of state transition. The results presented here suggest the role of ICS1 in integration of the chloroplast ultrastructure, the redox status of the plastoquinone pool, and organization of the photosystems, which all are important for optimal immune defence and light acclimatory responses. PMID:23956412
Optimization of crystal nucleation close to a metastable fluid-fluid phase transition.
Wedekind, Jan; Xu, Limei; Buldyrev, Sergey V; Stanley, H Eugene; Reguera, David; Franzese, Giancarlo
2015-06-22
The presence of a metastable fluid-fluid critical point is thought to dramatically influence the crystallization pathway, increasing the nucleation rate by many orders of magnitude over the predictions of classical nucleation theory. We use molecular dynamics simulations to study the kinetics of crystallization in the vicinity of this metastable critical point and throughout the metastable fluid-fluid phase diagram. To quantitatively understand how the fluid-fluid phase separation affects the crystal nucleation, we evaluate accurately the kinetics and reconstruct the thermodynamic free-energy landscape of crystal formation. Contrary to expectations, we find no special advantage of the proximity of the metastable critical point on the crystallization rates. However, we find that the ultrafast formation of a dense liquid phase causes the crystallization to accelerate both near the metastable critical point and almost everywhere below the fluid-fluid spinodal line. These results unveil three different scenarios for crystallization that could guide the optimization of the process in experiments.
Optimization of the transition path of the head hardening with using the genetic algorithms
NASA Astrophysics Data System (ADS)
Wróbel, Joanna; Kulawik, Adam
2016-06-01
An automated method of choice of the transition path of the head hardening in heat treatment process for the plane steel element is proposed in this communication. This method determines the points on the path of moving heat source using the genetic algorithms. The fitness function of the used algorithm is determined on the basis of effective stresses and yield point depending on the phase composition. The path of the hardening tool and also the area of the heat affected zone is determined on the basis of obtained points. A numerical model of thermal phenomena, phase transformations in the solid state and mechanical phenomena for the hardening process is implemented in order to verify the presented method. A finite element method (FEM) was used for solving the heat transfer equation and getting required temperature fields. The moving heat source is modeled with a Gaussian distribution and the water cooling is also included. The macroscopic model based on the analysis of the CCT and CHT diagrams of the medium-carbon steel is used to determine the phase transformations in the solid state. A finite element method is also used for solving the equilibrium equations giving us the stress field. The thermal and structural strains are taken into account in the constitutive relations.
Vargas, William E
2017-02-01
An accepted-probability-controlled simulated annealing (APCSA) method has shown to be a valuable tool to describe, in parametric form, by means of an extended Drude-Lorentz model, the dielectric function of several metals through infrared, visible, and ultraviolet photon energies [Appl. Opt.37, 5271 (1998)APOPAI0003-693510.1364/AO.37.005271]. In this work, an improved APCSA approach is used to estimate the parameters involved in an extended Drude-Lorentz type model which incorporates the dielectric constant due to a background electronic polarization in the Drude term and the normalization of the individual oscillation strengths involved in the Lorentz contributions to the dielectric function. This last approach allows us to introduce a new parameter z to be optimized: the number density ratio, i.e., the ratio between number density of conduction electrons and number density of metal ions. From the optimization of the z value within this novel approach, we evaluate other parameters: electrical resistivity, electron mean free path, effective mass of conduction electrons and relaxation time, Fermi energy, electronic density of states at the Fermi level, and electronic heat capacity coefficient. Application of the model is carried out to describe the dielectric functions of two transition metals, Pd and Zr, through ultraviolet, visible, and infrared photon energies.
Carver, Charles S.; Scheier, Michael F.; Segerstrom, Suzanne C.
2010-01-01
Optimism is an individual difference variable that reflects the extent to which people hold generalized favorable expectancies for their future. Higher levels of optimism have been related prospectively to better subjective well-being in times of adversity or difficulty (i.e., controlling for previous well-being). Consistent with such findings, optimism has been linked to higher levels of engagement coping and lower levels of avoidance, or disengagement, coping. There is evidence that optimism is associated with taking proactive steps to protect one's health, whereas pessimism is associated with health-damaging behaviors. Consistent with such findings, optimism is also related to indicators of better physical health. The energetic, task-focused approach that optimists take to goals also relates to benefits in the socioeconomic world. Some evidence suggests that optimism relates to more persistence in educational efforts and to higher later income. Optimists also appear to fare better than pessimists in relationships. Although there are instances in which optimism fails to convey an advantage, and instances in which it may convey a disadvantage, those instances are relatively rare. In sum, the behavioral patterns of optimists appear to provide models of living for others to learn from. PMID:20170998
Cornut, P-L; Soldermann, Y; Robin, C; Barranco, R; Kerhoas, A; Burillon, C
2013-12-01
To report the financial impact of using modern lens and vitreoretinal surgical techniques. Bottom-up sterilization and consumables costs for new surgical techniques (microincisional coaxial phacoemulsification and transconjunctival sutureless vitrectomy) and the corresponding former techniques (phacoemulsification with 3.2-mm incision and 20G vitrectomy) were determined. These costs were compared to each other and to the target costs of the Diagnosis Related Groups for public hospitals (Groupes Homogènes de Séjours [GHS]) concerned, extracted from the analytic accounting data of the French National Cost Study (Étude Nationale des Coûts [ENC]) for 2009 (target=sum of sterilization costs posted under medical logistics, consumables, implantable medical devices, and special pharmaceuticals posted as direct expenses). For outpatient lens surgery with or without vitrectomy (GHS code: 02C05J): the ENC's target cost for 2009 was 339€ out of a total of 1432€. The cost detailed in this study was 4 % higher than the target cost when the procedure was performed using the former technique (3.2mm sutured incision) and 12 % lower when the procedure was performed using the new technique (1.8mm sutureless) after removing now unnecessary consumables and optimization of the technique. For level I retinal detachment surgeries (GHS code: 02C021): the ENC's 2009 target cost was 641€ out of a total of 3091€. The cost specified in this study was 1 % lower than the target cost when the procedure was done using the former technique (20-G vitrectomy) and 16 % less when the procedure was performed using the new technique (transconjunctival vitrectomy) after removal of now unnecessary consumables and optimization of the technique. Contrary to generally accepted ideas, implementing modern techniques in ocular surgery can result in direct cost and sterilization savings when the operator takes advantage of the possibilities these techniques offer in terms of simplification of the
NASA Astrophysics Data System (ADS)
Batzias, Dimitris F.; Pollalis, Yannis A.
2012-12-01
In several cases, a competitive market can be simulated by a game, where each company/opponent is referred to as a player. In order to accommodate the fact that each player (alone or with alliances) is working against some others' interest, the rather conservative maximin criterion is frequently used for selecting the strategy or the combination of strategies that yield the best of the worst possible outcomes for each one of the players. Under this criterion, an optimal solution is obtained when neither player finds it beneficial to alter his strategy, which means that an equilibrium has been achieved, giving also the value of the game. If conditions change as regards a player, e.g., because of either achieving an unexpected successful result in developing an innovative industrial product or obtaining higher liquidity permitting him to increase advertisement in order to acquire a larger market share, then a new equilibrium is reached. The identification of the path between the old and the new equilibrium points may prove to be valuable for investigating the robustness of the solution by means of sensitivity analysis, since uncertainty plays a critical role in this situation, where evaluation of the payoff matrix is usually based on experts' estimates. In this work, the development of a standard methodology (including 16 activity stages and 7 decision nodes) for tracing this path is presented while a numerical implementation follows to prove its functionality.
Optimization of crystal nucleation close to a metastable fluid-fluid phase transition
Wedekind, Jan; Xu, Limei; Buldyrev, Sergey V.; Stanley, H. Eugene; Reguera, David; Franzese, Giancarlo
2015-01-01
The presence of a metastable fluid-fluid critical point is thought to dramatically influence the crystallization pathway, increasing the nucleation rate by many orders of magnitude over the predictions of classical nucleation theory. We use molecular dynamics simulations to study the kinetics of crystallization in the vicinity of this metastable critical point and throughout the metastable fluid-fluid phase diagram. To quantitatively understand how the fluid-fluid phase separation affects the crystal nucleation, we evaluate accurately the kinetics and reconstruct the thermodynamic free-energy landscape of crystal formation. Contrary to expectations, we find no special advantage of the proximity of the metastable critical point on the crystallization rates. However, we find that the ultrafast formation of a dense liquid phase causes the crystallization to accelerate both near the metastable critical point and almost everywhere below the fluid-fluid spinodal line. These results unveil three different scenarios for crystallization that could guide the optimization of the process in experiments PMID:26095898
NASA Astrophysics Data System (ADS)
Perera, Meeghage Madusanka
Layered transition Metal Dichalcogenides (TMDs) have demonstrated a wide range of remarkable properties for applications in next generation nano-electronics. These systems have displayed many "graphene-like" properties including a relatively high carrier mobility, mechanical flexibility, chemical and thermal stability, and moreover offer the significant advantage of a substantial band gap. However, the fabrication of high performance field-effect transistors (FETs) of TMDs is challenging mainly due to the formation of a significant Schottky barrier at metal/TMD interface in most cases. The main goal of this study is to develop novel contact engineering strategies to achieve low-resistance Ohmic contacts. Our first approach is to use Ionic Liquid (IL) gating of metal contacted MoS2 FETs to achieve highly transparent tunneling contacts due to the strong band banding at metal/MoS2 interface. The substantially reduced contact resistance in ionic-liquid-gated bilayer and few-layer MoS 2 FETs results in an ambipolar behavior with high ON/OFF ratios, a near-ideal subthreshold swing, and significantly improved field-effect mobility. Remarkably, the mobility of a 3-nm-thick MoS2 FET with an IL gate was found to increase from ˜ 100 cm2V-1s-1 to ˜ 220 cm2V-1s-1 as the temperature decreased from 180 K to 77 K. This finding is in quantitative agreement with the true channel mobility measured by four-terminal measurement, suggesting that the mobility is predominantly limited by phonon-scattering. To further improve the contacts of TMD devices, graphene was used as work function tunable electrodes. In order to achieve low Schottky barrier height, both IL gating and surface charge transfer doping were used to tune the work function of graphene electrodes close to the conduction band edge of MoS 2. As a result, the performance of our graphene contacted MoS2 FETs is limited by the channel rather than contacts, which is further verified by four-terminal measurements. Finally
NASA Astrophysics Data System (ADS)
Knop, R. A.; Aldering, G.; Amanullah, R.; Astier, P.; Blanc, G.; Burns, M. S.; Conley, A.; Deustua, S. E.; Doi, M.; Ellis, R.; Fabbro, S.; Folatelli, G.; Fruchter, A. S.; Garavini, G.; Garmond, S.; Garton, K.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I.; Howell, D. A.; Kim, A. G.; Lee, B. C.; Lidman, C.; Mendez, J.; Nobili, S.; Nugent, P. E.; Pain, R.; Panagia, N.; Pennypacker, C. R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schaefer, B.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Sullivan, M.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.
2003-11-01
We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z=0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM=0.25+0.07-0.06(statistical)+/-0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ=0.75+0.06-0.07(statistical)+/-0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w=-1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w=-1.05+0.15-0.20(statistical)+/-0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ>0)>0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution. Based in part on
Roy, Sudeshna; Šileikytė, Justina; Schiavone, Marco; Neuenswander, Benjamin; Argenton, Francesco; Aubé, Jeffrey; Hedrick, Michael P.; Chung, Thomas D. Y.
2015-01-01
The mitochondrial permeability transition pore (mtPTP) is a Ca2+-requiring mega-channel which, under pathological conditions, leads to the deregulated release of Ca2+ and mitochondrial dysfunction, ultimately resulting in cell death. Although the mtPTP is a potential therapeutic target for many human pathologies, its potential as a drug target is currently unrealized. Herein we describe an optimization effort initiated around hit 1, 5-(3-hydroxyphenyl)-N-(3,4,5-trimethoxyphenyl)isoxazole-3-carboxamide, which was found to possess promising inhibitory activity against mitochondrial swelling (EC50 < 0.39 µm) and showed no interference on the inner mitochondrial membrane potential (rhodamine 123 uptake EC50 > 100 µm). This enabled the construction of a series of picomolar mtPTP inhibitors that also potently increase the calcium retention capacity of the mitochondria. Finally, the therapeutic potential and in vivo efficacy of one of the most potent analogues, N-(3-chloro-2-methylphenyl)-5-(4-fluoro-3-hydroxyphenyl)isoxazole-3-carboxamide (60), was validated in a biologically relevant zebrafish model of collagen VI congenital muscular dystrophies. PMID:26286375
Roy, Sudeshna; Šileikytė, Justina; Schiavone, Marco; Neuenswander, Benjamin; Argenton, Francesco; Aubé, Jeffrey; Hedrick, Michael P; Chung, Thomas D Y; Forte, Michael A; Bernardi, Paolo; Schoenen, Frank J
2015-10-01
The mitochondrial permeability transition pore (mtPTP) is a Ca(2+) -requiring mega-channel which, under pathological conditions, leads to the deregulated release of Ca(2+) and mitochondrial dysfunction, ultimately resulting in cell death. Although the mtPTP is a potential therapeutic target for many human pathologies, its potential as a drug target is currently unrealized. Herein we describe an optimization effort initiated around hit 1, 5-(3-hydroxyphenyl)-N-(3,4,5-trimethoxyphenyl)isoxazole-3-carboxamide, which was found to possess promising inhibitory activity against mitochondrial swelling (EC50 <0.39 μM) and showed no interference on the inner mitochondrial membrane potential (rhodamine 123 uptake EC50 >100 μM). This enabled the construction of a series of picomolar mtPTP inhibitors that also potently increase the calcium retention capacity of the mitochondria. Finally, the therapeutic potential and in vivo efficacy of one of the most potent analogues, N-(3-chloro-2-methylphenyl)-5-(4-fluoro-3-hydroxyphenyl)isoxazole-3-carboxamide (60), was validated in a biologically relevant zebrafish model of collagen VI congenital muscular dystrophies.
Fukuoka, Yoshiyuki; Horiuchi, Masahiro
2017-01-01
Energy cost of transport per unit distance (CoT; J·kg-1·km-1) displays a U-shaped fashion in walking and a linear fashion in running as a function of gait speed (v; km·h-1). There exists an intersection between U-shaped and linear CoT-v relationships, being termed energetically optimal transition speed (EOTS; km·h-1). Combined effects of gradient and moderate normobaric hypoxia (15.0% O2) were investigated when walking and running at the EOTS in fifteen young males. The CoT values were determined at eight walking speeds (2.4–7.3 km·h-1) and four running speeds (7.3–9.4 km·h-1) on level and gradient slopes (±5%) at normoxia and hypoxia. Since an alteration of tibialis anterior (TA) activity has been known as a trigger for gait transition, electromyogram was recorded from TA and its antagonists (gastrocnemius medialis (GM) and gastrocnemius lateralis (GL)) for about 30 steps during walking and running corresponding to the individual EOTS in each experimental condition. Mean power frequency (MPF; Hz) of each muscle was quantified to evaluate alterations of muscle fiber recruitment pattern. The EOTS was not significantly different between normoxia and hypoxia on any slopes (ranging from 7.412 to 7.679 km·h-1 at normoxia and 7.516 to 7.678 km·h-1 at hypoxia) due to upward shifts (enhanced metabolic rate) of both U-shaped and linear CoT-v relationships at hypoxia. GM, but not GL, activated more when switching from walking to running on level and gentle downhill slopes. Significant decreases in the muscular activity and/or MPF were observed only in the TA when switching the gait pattern. Taken together, the EOTS was not slowed by moderate hypoxia in the population of this study. Muscular activities of lower leg extremities and those muscle fiber recruitment patterns are dependent on the gradient when walking and running at the EOTS. PMID:28301525
Abe, Daijiro; Fukuoka, Yoshiyuki; Horiuchi, Masahiro
2015-01-01
The oxygen cost of transport per unit distance (CoT; mL·kg-1·km-1) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg-1·min-1) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h-1. The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h-1) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h-1, P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h-1, P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h-1, P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h-1, P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study. PMID:26383249
Szefczyk, Borys; Mulholland, Adrian J; Ranaghan, Kara E; Sokalski, W Andrzej
2004-12-15
Chorismate mutase is a key model system in the development of theories of enzyme catalysis. To analyze the physical nature of catalytic interactions within the enzyme active site and to estimate the stabilization of the transition state (TS) relative to the substrate (differential transition state stabilization, DTSS), we have carried out nonempirical variation-perturbation analysis of the electrostatic, exchange, delocalization, and correlation interactions of the enzyme-bound substrate and transition-state structures derived from ab initio QM/MM modeling of Bacillus subtilis chorismate mutase. Significant TS stabilization by approximately -23 kcal/mol [MP2/6-31G(d)] relative to the bound substrate is in agreement with that of previous QM/MM modeling and contrasts with suggestions that catalysis by this enzyme arises purely from conformational selection effects. The most important contributions to DTSS come from the residues, Arg90, Arg7, Glu78, a crystallographic water molecule, Arg116, and Arg63, and are dominated by electrostatic effects. Analysis of the differential electrostatic potential of the TS and substrate allows calculation of the catalytic field, predicting the optimal location of charged groups to achieve maximal DTSS. Comparison with the active site of the enzyme from those of several species shows that the positions of charged active site residues correspond closely to the optimal catalytic field, showing that the enzyme has evolved specifically to stabilize the TS relative to the substrate.
SANS study of vortex lattice structural transition in optimally doped (Ba1-x K x )Fe2As2
NASA Astrophysics Data System (ADS)
Demirdiş, S.; van der Beek, C. J.; Mühlbauer, S.; Su, Y.; Wolf, Th
2016-10-01
Small-angle neutron scattering on high quality single crystalline Ba1-x K x Fe2As2 reveals the transition from a low-field vortex solid phase with orientational order to a vortex polycrystal at high magnetic field. The vortex order-disorder transition is correlated with the second-peak feature in isothermal hysteresis loops, and is interpreted in terms of the generation of supplementary vortex solid dislocations. The sharp drop of the structure factor above the second peak field is explained by the dynamics of freezing of the vortex ensemble in the high field phase.
SANS study of vortex lattice structural transition in optimally doped (Ba1-x K x )Fe2As2.
Demirdiş, S; van der Beek, C J; Mühlbauer, S; Su, Y; Wolf, Th
2016-10-26
Small-angle neutron scattering on high quality single crystalline Ba1-x K x Fe2As2 reveals the transition from a low-field vortex solid phase with orientational order to a vortex polycrystal at high magnetic field. The vortex order-disorder transition is correlated with the second-peak feature in isothermal hysteresis loops, and is interpreted in terms of the generation of supplementary vortex solid dislocations. The sharp drop of the structure factor above the second peak field is explained by the dynamics of freezing of the vortex ensemble in the high field phase.
NASA Astrophysics Data System (ADS)
Shirage, Parasharam M.; Miyazawa, Kiichi; Kihou, Kunihiro; Kito, Hijiri; Yoshida, Yoshiyuki; Tanaka, Yasumoto; Eisaki, Hiroshi; Iyo, Akira
2010-07-01
We report the iron (Fe) isotope effect on the transition temperature (Tc) in oxygen-deficient SmFeAsO1-y, a 50-K-class, Fe-based superconductor. For the optimally doped samples with Tc=54K, a change of the average atomic mass of Fe (MFe) causes a negligibly small shift in Tc, with the Fe isotope coefficient (αFe) as small as -0.024±0.015 (where αFe=-dlnTc/dlnMFe). This result contrasts with the finite, inverse isotope shift observed in optimally doped (Ba,K)Fe2As2, indicating that the contribution of the electron-phonon interaction markedly differs between these two Fe-based high-Tc superconductors.
Wahba, Roger; Kleinert, Robert; Hellmich, Martin; Heiermann, Nadine; Dieplinger, Georg; Schlößer, Hans A; Buchner, Denise; Kurschat, Christine; Stippel, Dirk L
2017-06-01
Optimizing a living kidney donation program is important to guarantee a high grade of acceptance among potential donors. Hand-assisted retroperitoneoscopic donor nephrectomy (HARP) is an alternative to the open anterior approach (AA) technique. Problems associated to the learning curve could hinder a transition. 3D display technique seems to ease minimally invasive surgery. Aim of this study was to evaluate the learning curve during the transition from AA to HARP and the influence of the 3D display system on the established technique. Observational study (n = 207) during transition to HARP and introduction of 3D display technique. Operation time (OT), warm ischemia time (WIT) and blood loss (BL) of HARP decreased during transition. Pairwise group comparison for OT showed a significant learning effect for the first 30 out of 50 HARPs without influence on graft function. Between AA and HARP no significant difference in OT (133 ± 24 vs. 127 ± 19 min, p = 0.25) but for WIT (23 ± 28 vs. 126 ± 40 s, p < 0.005) and BL (328 ± 207 vs. 54 ± 35 ml, p < 0.005) was seen. There was neither a significant difference in donors' nor recipients' eGFR. OT (98 ± 16 vs. 106 ± 19 min, p = 0.036) and WIT (97 ± 37 vs. 120 ± 57 s, p = 0.023) were significantly shorter for the 3D technique compared to 2D. A transition to HARP is possible without additional risk for the donor or loss of quality for the recipient. The learning curve for HARP is steep and short. The introduction of 3D display technique after transition facilitates the surgical preparation and could further help to optimize HARP.
Boyd, Nicola Jane; Wilson, Mark R
2015-10-14
The physical properties and phase transitions of thermotropic liquid crystals are highly sensitive to small changes in chemical structure. However, these changes are challenging to model, as both the phase diagram and mesophase properties obtained from fully atomistic simulations are strongly dependent on the force field model employed, and the current generation of chemical force fields has not proved accurate enough to provide reliable predictions of transition temperatures for many liquid crystals. This paper presents a strategy for improving the nematic clearing point, TNI, in atomistic simulations, by systematic optimization of the General Amber Force Field (GAFF) for key mesogenic fragments. We show that with careful optimization of the parameters describing a series of liquid crystal fragment molecules, it is possible to transfer these parameters to larger liquid crystal molecules and make accurate predictions for nematic mesophase formation. This new force field, GAFF-LCFF, is used to predict the nematic-isotropic clearing point to within 5 °C for the nematogen 1,3-benzenedicarboxylic acid,1,3-bis(4-butylphenyl)ester, an improvement of 60 °C over the standard GAFF force field.
Cadieu, F.J.
1992-08-01
Progress is reported in three areas: high coercivity Sm-Fe-Ti-V, Sm-Fe-Zr, and two element Sm-Fe Sm{sub 5}(Fe,T){sub 17} type crystalline phases; ThMn{sub 12} type pseudobinary SmFe{sub 12-x}T{sub x}(0{le}{times}{le}1.5); and sputter process control for the synthesis of precisely textured rare earth-transition metal magnetic films. (DLC)
Ye, Hui; Zhu, Lin; Wang, Lin; Liu, Huiying; Zhang, Jun; Wu, Mengqiu; Wang, Guangji; Hao, Haiping
2016-02-11
Multiple reaction monitoring (MRM) is a universal approach for quantitative analysis because of its high specificity and sensitivity. Nevertheless, optimization of MRM parameters remains as a time and labor-intensive task particularly in multiplexed quantitative analysis of small molecules in complex mixtures. In this study, we have developed an approach named Stepped MS(All) Relied Transition (SMART) to predict the optimal MRM parameters of small molecules. SMART requires firstly a rapid and high-throughput analysis of samples using a Stepped MS(All) technique (sMS(All)) on a Q-TOF, which consists of serial MS(All) events acquired from low CE to gradually stepped-up CE values in a cycle. The optimal CE values can then be determined by comparing the extracted ion chromatograms for the ion pairs of interest among serial scans. The SMART-predicted parameters were found to agree well with the parameters optimized on a triple quadrupole from the same vendor using a mixture of standards. The parameters optimized on a triple quadrupole from a different vendor was also employed for comparison, and found to be linearly correlated with the SMART-predicted parameters, suggesting the potential applications of the SMART approach among different instrumental platforms. This approach was further validated by applying to simultaneous quantification of 31 herbal components in the plasma of rats treated with a herbal prescription. Because the sMS(All) acquisition can be accomplished in a single run for multiple components independent of standards, the SMART approach are expected to find its wide application in the multiplexed quantitative analysis of complex mixtures.
NASA Astrophysics Data System (ADS)
Pahlavani, M. R.; Firoozi, B.
2015-11-01
Within a developed particle-hole approach, a systematic study of the β- transition from the ground state of the 16N nucleus to the ground and some exited states of the 16O nucleus has been carried out. The energy spectrum and the wave functions of pure configuration of the 16N and 16O nuclei are numerically obtained using the mean-field shell model with respect to the Woods-Saxon nuclear potential accompanying spin-orbit and Coulomb interaction. Considering SDI residual interaction, mixed configuration of ground and excited pnTDA and TDA states are extracted for the aforementioned nucleus. These energy spectra and corresponding eigenstates are highly correspondent to the experimental energy spectrum and eigenstates after adjusting the residual potential parameters using the Nelder-Mead (NM) algorithm. In this approach, the endpoint energy, log ft and the partial half-lives of some possible transitions are calculated. The obtained results using the optimized SDI approach are reasonably close to the available experimental data.
NASA Astrophysics Data System (ADS)
Skelton, J. M.; Elliott, S. R.
2013-05-01
Phase-change materials are the alloys at the heart of an emerging class of next-generation, non-volatile digital memory technologies. However, the widely studied Ge-Sb-Te system possesses several undesirable properties, and enhancing its properties, e.g. by doping, is an area of active research. Various first-row transition-metal dopants have been shown to impart useful property enhancements, but a systematic study of the entire period has yet to be undertaken, and little has been done to investigate their interaction with the host material at the atomic level. We have carried out first-principles computer simulations of the complete phase-change cycle in Ge2Sb2Te5 doped with each of the ten first-row transition metals. In this article, we present a comprehensive survey of the electronic, magnetic and optical properties of these doped materials. We discuss in detail their atomic-level structure, and relate the microscopic behaviours of the dopant atoms to their influence on the Ge2Sb2Te5 host. By considering an entire family of similar materials, we identify trends and patterns which might be used to predict suitable dopants for optimizing materials for specific phase-change applications. The computational method employed here is general, and this materials-discovery approach could be applied in the future to study other families of potential dopants for such materials.
Skelton, J M; Elliott, S R
2013-05-22
Phase-change materials are the alloys at the heart of an emerging class of next-generation, non-volatile digital memory technologies. However, the widely studied Ge-Sb-Te system possesses several undesirable properties, and enhancing its properties, e.g. by doping, is an area of active research. Various first-row transition-metal dopants have been shown to impart useful property enhancements, but a systematic study of the entire period has yet to be undertaken, and little has been done to investigate their interaction with the host material at the atomic level. We have carried out first-principles computer simulations of the complete phase-change cycle in Ge2Sb2Te5 doped with each of the ten first-row transition metals. In this article, we present a comprehensive survey of the electronic, magnetic and optical properties of these doped materials. We discuss in detail their atomic-level structure, and relate the microscopic behaviours of the dopant atoms to their influence on the Ge2Sb2Te5 host. By considering an entire family of similar materials, we identify trends and patterns which might be used to predict suitable dopants for optimizing materials for specific phase-change applications. The computational method employed here is general, and this materials-discovery approach could be applied in the future to study other families of potential dopants for such materials.
Francis, S T; Bowtell, R; Gowland, P A
2008-02-01
This work describes a new compartmental model with step-wise temporal analysis for a Look-Locker (LL)-flow-sensitive alternating inversion-recovery (FAIR) sequence, which combines the FAIR arterial spin labeling (ASL) scheme with a LL echo planar imaging (EPI) measurement, using a multireadout EPI sequence for simultaneous perfusion and T*(2) measurements. The new model highlights the importance of accounting for the transit time of blood through the arteriolar compartment, delta, in the quantification of perfusion. The signal expected is calculated in a step-wise manner to avoid discontinuities between different compartments. The optimal LL-FAIR pulse sequence timings for the measurement of perfusion with high signal-to-noise ratio (SNR), and high temporal resolution at 1.5, 3, and 7T are presented. LL-FAIR is shown to provide better SNR per unit time compared to standard FAIR. The sequence has been used experimentally for simultaneous monitoring of perfusion, transit time, and T*(2) changes in response to a visual stimulus in four subjects. It was found that perfusion increased by 83 +/- 4% on brain activation from a resting state value of 94 +/- 13 ml/100 g/min, while T*(2) increased by 3.5 +/- 0.5%. (c) 2008 Wiley-Liss, Inc.
NASA Astrophysics Data System (ADS)
Nath, Bikram; Mondal, Chandan Kumar
2014-08-01
We have designed and optimised a combined laser pulse using optimal control theory-based adaptive simulated annealing technique for selective vibrational excitations and photo-dissociation. Since proper choice of pulses for specific excitation and dissociation phenomena is very difficult, we have designed a linearly combined pulse for such processes and optimised the different parameters involved in those pulses so that we can get an efficient combined pulse. The technique makes us free from choosing any arbitrary type of pulses and makes a ground to check their suitability. We have also emphasised on how we can improve the performance of simulated annealing technique by introducing an adaptive step length of the different variables during the optimisation processes. We have also pointed out on how we can choose the initial temperature for the optimisation process by introducing heating/cooling step to reduce the annealing steps so that the method becomes cost effective.
NASA Astrophysics Data System (ADS)
Li, Zhipeng; Yi, Yi
2014-07-01
In this paper, traffic states and jamming transitions on two-lane highway including a bus are studied by using a car following model with a calibrated optimal velocity function. We derive a new flow-density diagram with four distinctly separated traffic states, which is different from that of the earlier study obtained by applying the OVM with theoretical optimal velocity function. The spatio-temporal diagrams are presented to illustrate phase characteristics of each traffic state. It is found that the phase characteristic features of two of four states are different from any state of the earlier result, and traffic flow of state 2 and state 3 can reproduce some characteristics observed from empirical investigations such as centralized lane-changing, hanging tail of cluster, and synchronized flow. In addition, we have clarified the lane-changing behaviors and their effects on two-lane traffic flow including a bus. It is shown that the velocity oscillations behind the bus can help the lane-changing in state 2 and the behaviors of lane-changing are the important reason of forming of the synchronized flow in state 3. It is also concluded that lane-changing can only improve the current in the region of middle density.
Yang, Siu Ming; Lo, Chor Man
2011-01-01
BACKGROUND: This study aimed to evaluate emergency medicine doctors’ accuracy in predicting the need of film printing in a simulated setting of computed radiography and assess whether this can facilitate optimal patient care. METHODS: Cross sectional study was conducted from 20 March 2009 to 3 April 2009 in 1334 patients. After clinical assessment of those patients who needed X-ray examination, doctors in the emergency department would indicate whether film printing was necessary for subsequent patient care in a simulated computed radiography setting. The final discharge plan was then retrieved from each patient record. Accuracy of doctors’ prediction was calculated by comparing the initial request for radiographic film printing and the final need of film. Doctors with different level of emergency medicine experience would also be analyzed and compared. RESULTS: The sensitivity of predicting film printing was 84.5% and the specificity of predicting no film printing was 91.2%. Positive predictive value was 88.4% while negative predictive value was 88.2%. The overall accuracy was 88.2%. The accuracy of doctors stratified into groups of fellows, higher trainees and basic trainees were 85.4%, 90.5% and 88.5% respectively (P=0.073). CONCLUSIONS: Our study showed that doctors can reliably predict whether film printing is needed after clinical assessment of patients, before actual image viewing. Advanced indication for film printing at the time of imaging request for selected patients can save time for all parties with minimal wastage. PMID:25214980
Strong Combination of Ant Colony Optimization with Constraint Programming Optimization
NASA Astrophysics Data System (ADS)
Khichane, Madjid; Albert, Patrick; Solnon, Christine
We introduce an approach which combines ACO (Ant Colony Optimization) and IBM ILOG CP Optimizer for solving COPs (Combinatorial Optimization Problems). The problem is modeled using the CP Optimizer modeling API. Then, it is solved in a generic way by a two-phase algorithm. The first phase aims at creating a hot start for the second: it samples the solution space and applies reinforcement learning techniques as implemented in ACO to create pheromone trails. During the second phase, CP Optimizer performs a complete tree search guided by the pheromone trails previously accumulated. The first experimental results on knapsack, quadratic assignment and maximum independent set problems show that this new algorithm enhances the performance of CP Optimizer alone.
Optimally combined confidence limits
NASA Astrophysics Data System (ADS)
Janot, P.; Le Diberder, F.
1998-02-01
An analytical and optimal procedure to combine statistically independent sets of confidence levels on a quantity is presented. This procedure does not impose any constraint on the methods followed by each analysis to derive its own limit. It incorporates the a priori statistical power of each of the analyses to be combined, in order to optimize the overall sensitivity. It can, in particular, be used to combine the mass limits obtained by several analyses searching for the Higgs boson in different decay channels, with different selection efficiencies, mass resolution and expected background. It can also be used to combine the mass limits obtained by several experiments (e.g. ALEPH, DELPHI, L3 and OPAL, at LEP 2) independently of the method followed by each of these experiments to derive their own limit. A method to derive the limit set by one analysis is also presented, along with an unbiased prescription to optimize the expected mass limit in the no-signal-hypothesis.
Integrated Network Decompositions and Dynamic Programming for Graph Optimization (INDDGO)
2012-05-31
The INDDGO software package offers a set of tools for finding exact solutions to graph optimization problems via tree decompositions and dynamic programming algorithms. Currently the framework offers serial and parallel (distributed memory) algorithms for finding tree decompositions and solving the maximum weighted independent set problem. The parallel dynamic programming algorithm is implemented on top of the MADNESS task-based runtime.
Optimization on magnetic transitions and magnetostriction in TbxDyyNdz(Fe0.9Co0.1)1.93 compounds
NASA Astrophysics Data System (ADS)
Hu, C. C.; Shi, Y. G.; Shi, D. N.; Zhou, X. G.; Fan, J. Y.; Lv, L. Y.; Tang, S. L.
2013-10-01
The structure, magnetic transitions, and magnetostriction of TbxDyyNdz(Fe0.9Co0.1)1.93 polycrystalline compounds have been investigated, with the ratio of x, y, and z spanning the line of minimum magnetic anisotropy. Anisotropy compensation with lower Tb content was realized in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound. The spin configuration diagram accompanied with different crystal structures was constructed to illustrate the arrangement for the easy magnetization direction and crystal structure. An optimized effect on magnetostriction especially at the relatively low field of 1 kOe (197 ppm) was observed in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound, which is about two times larger than that of the sample free of Nd (62 ppm). Meanwhile, the polycrystalline saturation magnetostriction (λs=945 ppm) of Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 is even much larger than that of the Ho-doped multicomponent single crystal compound Tb0.2Dy0.22Ho0.58Fe2 (λs=530 ppm). Low content of heavy rare earth Tb, high Curie temperature, and large ratio between magnetostriction and the absolute value of the first anisotropy constant λa/|K1| were obtained in Tb0.253Dy0.657Nd0.09(Fe0.9Co0.1)1.93 compound, which may make it a potential material for magnetostrictive application.
Variational Transition State Theory
Truhlar, Donald G.
2016-09-29
This is the final report on a project involving the development and applications of variational transition state theory. This project involved the development of variational transition state theory for gas-phase reactions, including optimized multidimensional tunneling contributions and the application of this theory to gas-phase reactions with a special emphasis on developing reaction rate theory in directions that are important for applications to combustion. The development of variational transition state theory with optimized multidimensional tunneling as a useful computational tool for combustion kinetics involved eight objectives.
Gravitationally induced quantum transitions
NASA Astrophysics Data System (ADS)
Landry, A.; Paranjape, M. B.
2016-06-01
In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω . The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as t2. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of 1.06 ×10-5, and hence with a million ultracold neutrons, one should be able to observe transitions.
ERIC Educational Resources Information Center
Statfeld, Jenna L.
2011-01-01
Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…
Hu, Ding; Lu, Xingye; Zhang, Wenliang; Luo, Huiqian; Li, Shiliang; Wang, Peipei; Chen, Genfu; Han, Fei; Banjara, Shree R.; Sapkota, A.; Kreyssig, A.; Goldman, A. I.; Yamani, Z.; Niedermayer, Christof; Skoulatos, Markos; Georgii, Robert; Keller, T.; Wang, Pengshuai; Yu, Weiqiang; Dai, Pengcheng
2015-04-17
In this study, we use nuclear magnetic resonance (NMR), high-resolution x-ray and neutron scattering to study structural and magnetic phase transitions in phosphorus-doped BaFe_{2}(As_{1-x}P_{x})_{2}. Thus, previous transport, NMR, specific heat, and magnetic penetration depth measurements have provided compelling evidence for the presence of a quantum critical point (QCP) near optimal superconductivity at x = 0.3. However, we show that the tetragonal-to-orthorhombic structural (T_{s}) and paramagnetic to antiferromagnetic (AF, T_{N}) transitions in BaFe_{2}(As_{1-x}P_{x})_{2} are always coupled and approach to T_{N} ≈ T_{s} ≥ T_{c} (≈ 29 K) for x = 0.29 before vanishing abruptly for x ≥ 0.3. These results suggest that AF order in BaFe_{2}(As_{1-x}P_{x})_{2} disappears in a weakly first order fashion near optimal superconductivity, much like the electron-doped iron pnictides with an avoided QCP.
NASA Astrophysics Data System (ADS)
Burtsev, V. A.; Kalinin, N. V.; Vaganov, S. A.
2017-01-01
Electrical characteristics of low-inductance capillary-type discharge have been determined by numerical model calculations, which ensure high efficiency of energy supply to a plasma column with an aspect ratio of 1: 100. The EUV argon laser based on this discharge provides a gain of g + > 1 cm-1 on the operating transition and ensures single-pass spontaneous lasing with g + l > 25 (where l is the active medium length).
Scott, Michael J; McEvoy, Matthew D; Gordon, Debra B; Grant, Stuart A; Thacker, Julie K M; Wu, Christopher L; Gan, Tong J; Mythen, Monty G; Shaw, Andrew D; Miller, Timothy E
2017-01-01
Within an enhanced recovery pathway (ERP), the approach to treating pain should be multifaceted and the goal should be to deliver "optimal analgesia", which we define in this paper as a technique that optimizes patient comfort and facilitates functional recovery with the fewest medication side effects. With input from a multidisciplinary, international group of experts and through a structured review of the literature and use of a modified Delphi method, we achieved consensus surrounding the topic of optimal analgesia in the perioperative period for colorectal surgery patients. As a part of the first Perioperative Quality Improvement (POQI) workgroup meeting, we sought to develop a consensus document describing a comprehensive, yet rational and practical, approach for developing an evidence-based plan for achieving optimal analgesia, specifically for a colorectal surgery within an ERP. The goal was twofold: (a) that application of this process would lead to improved patient outcomes and (b) that investigation of the questions raised would identify knowledge gaps to aid the direction for research into analgesia within ERPs in the years to come. This document details the evidence for a wide range of analgesic components, with particular focus on care in the post-anesthesia care unit, general care ward, and transition to home after discharge. The preoperative and operative consensus statement for analgesia was covered in Part 1 of this paper. The overall conclusion is that the combination of analgesic techniques employed in the perioperative period is not important as long as it is effective in delivering the goal of "optimal analgesia" as set forth in this document.
López Arvizu, Gregorio; Calaminici, Patrizia
2007-05-21
Density functional calculations have been performed for small nickel clusters, Ni(n), Ni(n) (+), and Ni(n)(-) (n
Parallel Algorithms for Graph Optimization using Tree Decompositions
Sullivan, Blair D; Weerapurage, Dinesh P; Groer, Christopher S
2012-06-01
Although many $\\cal{NP}$-hard graph optimization problems can be solved in polynomial time on graphs of bounded tree-width, the adoption of these techniques into mainstream scientific computation has been limited due to the high memory requirements of the necessary dynamic programming tables and excessive runtimes of sequential implementations. This work addresses both challenges by proposing a set of new parallel algorithms for all steps of a tree decomposition-based approach to solve the maximum weighted independent set problem. A hybrid OpenMP/MPI implementation includes a highly scalable parallel dynamic programming algorithm leveraging the MADNESS task-based runtime, and computational results demonstrate scaling. This work enables a significant expansion of the scale of graphs on which exact solutions to maximum weighted independent set can be obtained, and forms a framework for solving additional graph optimization problems with similar techniques.
Martens, Koen; Aetukuri, Nagaphani; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.
2014-02-24
Key to the growth of epitaxial, atomically thin films is the preparation of the substrates on which they are deposited. Here, we report the growth of atomically smooth, ultrathin films of VO{sub 2} (001), only ∼2 nm thick, which exhibit pronounced metal-insulator transitions, with a change in resistivity of ∼500 times, at a temperature that is close to that of films five times thicker. These films were prepared by pulsed laser deposition on single crystalline TiO{sub 2}(001) substrates that were treated by dipping in acetone, HCl and HF in successive order, followed by an anneal at 700–750 °C in flowing oxygen. This pretreatment removes surface contaminants, TiO{sub 2} defects, and provides a terraced, atomically smooth surface.
Dermish, Amna I; Turok, David K
2013-07-01
Worldwide, 40% of all pregnancies are unintended. Widespread, over-the-counter availability of oral emergency contraception (EC) has not reduced unintended pregnancy rates. The EC visit presents an opportunity to initiate a highly effective method of contraception in a population at high risk of unintended pregnancy who are actively seeking to avoid pregnancy. The copper intrauterine device (IUD), the most effective method of EC, continues to provide contraception as effective as sterilization for up to 12 years, and it should be offered as the first-line method of EC wherever possible. Increased demand for and supply of the copper IUD for EC may have an important role in reducing rates of unintended pregnancy. The EC visit should include access to the copper IUD as optimal care but should ideally include access to all highly effective methods of contraception.
Fouad, Nadya A; Bynner, John
2008-01-01
Individuals make choices in, and adjust to, a world of work that is often a moving target. Because work is so central to human functioning, and transitions in and out of work can have major mental health repercussions, the authors argue that applied psychologists in health services need to understand those transitions. This article focuses on the different types of transition throughout a person's working life and the resources needed at different stages to ensure the success of these transitions. The authors start by examining the roles of capability and adaptability in supporting and facilitating adjustment to work transitions and their relation to identity development. They then examine the role of social and institutional contexts in shaping work transitions and their outcomes. The authors focus on voluntary versus involuntary transitions and then broaden the lens in discussing the policy implications of research on work transitions.
Aklujkar, Muktak; Prince, Roger C; Beatty, J Thomas
2005-05-15
A conserved orf of previously unknown function (herein designated as puhE) is located 3' of the reaction centre H (puhA) gene in purple photosynthetic bacteria, in the order puhABCE in Rhodobacter capsulatus. Disruptions of R. capsulatus puhE resulted in a long lag in the growth of photosynthetic cultures inoculated with cells grown under high aeration, and increased the level of the peripheral antenna, light-harvesting complex 2 (LH2). The amount of the photosynthetic reaction centre (RC) and its core antenna, light-harvesting complex 1 (LH1), was reduced; however, there was no decrease in expression of a lacZ reporter fused to the puf (RC and LH1) promoter, in RC assembly in the absence of LH1, or in LH1 assembly in the absence of the RC. In strains that lack LH2, disruption of puhE increased the in vivo absorption at 780 nm, which we attribute to excess bacteriochlorophyll a (BChl) pigment production. This effect was seen in the presence and absence of PufQ, a protein that stimulates BChl biosynthesis. Expression of puhE from a plasmid reduced A(780) production in puhE mutants. We suggest that PuhE modulates BChl biosynthesis independently of PufQ, and that the presence of excess BChl in PuhE(-)LH2(+) strains results in excess LH2 assembly and also interferes with the adaptation of cells during the transition from aerobic respiratory to anaerobic photosynthetic growth.
de Wind, Astrid; Geuskens, Goedele A; Ybema, Jan Fekke; Bongers, Paulien M; van der Beek, Allard J
2015-01-01
Determinants in the domains health, job characteristics, skills, and social and financial factors may influence early retirement through three central explanatory variables, namely, the ability, motivation, and opportunity to work. Based on the literature, we created the Early Retirement Model. This study aims to investigate whether data support the model and how it could be improved. Employees aged 58-62 years (N=1862), who participated in the first three waves of the Dutch Study on Transitions in Employment, Ability and Motivation (STREAM) were included. Determinants were assessed at baseline, central explanatory variables after one year, and early retirement after two years. Structural equation modeling was applied. Testing the Early Retirement Model resulted in a model with good fit. Health, job characteristics, skills, and social and financial factors were related to the ability, motivation and/or opportunity to work (significant β range: 0.05-0.31). Lower work ability (β=-0.13) and less opportunity to work (attitude colleagues and supervisor about working until age 65: β=-0.24) predicted early retirement, whereas the motivation to work (work engagement) did not. The model could be improved by adding direct effects of three determinants on early retirement, ie, support of colleagues and supervisor (β=0.14), positive attitude of the partner with respect to early retirement (β=0.15), and not having a partner (β=-0.13). The Early Retirement Model was largely supported by the data but could be improved. The prolongation of working life might be promoted by work-related interventions focusing on health, work ability, the social work climate, social norms on prolonged careers, and the learning environment.
2012-06-05
It appeared that New Yorkers were not going to be able to see the transit of the planet Venus across the Sun, but just before the transit was over the sun broke through the clouds and Yvette Lee Kang was able to catch a glimpse of the transit on Tuesday, June 5, 2012 in New York. A transit of Venus occurs when the planet passes directly between the sun and earth. This alignment is rare, coming in pairs that are eight years apart but separated by over a century. The next Venus transit will be in December 2117. Photo Credit: (NASA/Bill Ingalls)
2012-06-05
It appeared that New Yorkers were not going to be able to see the transit of the planet Venus across the Sun, but just before the transit was over the sun broke through the clouds and Liz Heller and Andriel Mesznik were able to catch a glimpse of the transit on Tuesday, June 5, 2012 in New York. A transit of Venus occurs when the planet passes directly between the sun and earth. This alignment is rare, coming in pairs that are eight years apart but separated by over a century. The next Venus transit will be in December 2117. Photo Credit: (NASA/Bill Ingalls)
Transition States and transition state analogue interactions with enzymes.
Schramm, Vern L
2015-04-21
evolved enzymatic geometry to form the transition state. Evolution to efficient catalysis optimized this geometry and its stabilization by a transition state mimic results in tight binding. Release rates of transition state analogues are orders of magnitude slower than product release in normal catalytic function. During catalysis, product release is facilitated by altered chemistry. Compared to the weak associations found in Michaelis complexes, transition state analogues involve strong interactions related to those in the transition state. Optimum binding of transition state analogues occurs when the complex retains the system motions intrinsic to transition state formation. Conserved dynamic motion retains the entropic components of inhibitor complexes, improving the thermodynamics of analogue binding.
Network observability transitions.
Yang, Yang; Wang, Jianhui; Motter, Adilson E
2012-12-21
In the modeling, monitoring, and control of complex networks, a fundamental problem concerns the comprehensive determination of the state of the system from limited measurements. Using power grids as example networks, we show that this problem leads to a new type of percolation transition, here termed a network observability transition, which we solve analytically for the configuration model. We also demonstrate a dual role of the network's community structure, which both facilitates optimal measurement placement and renders the networks substantially more sensitive to "observability attacks." Aside from their immediate implications for the development of smart grids, these results provide insights into decentralized biological, social, and technological networks.
Optimally Stopped Optimization
NASA Astrophysics Data System (ADS)
Vinci, Walter; Lidar, Daniel A.
2016-11-01
We combine the fields of heuristic optimization and optimal stopping. We propose a strategy for benchmarking randomized optimization algorithms that minimizes the expected total cost for obtaining a good solution with an optimal number of calls to the solver. To do so, rather than letting the objective function alone define a cost to be minimized, we introduce a further cost-per-call of the algorithm. We show that this problem can be formulated using optimal stopping theory. The expected cost is a flexible figure of merit for benchmarking probabilistic solvers that can be computed when the optimal solution is not known and that avoids the biases and arbitrariness that affect other measures. The optimal stopping formulation of benchmarking directly leads to a real-time optimal-utilization strategy for probabilistic optimizers with practical impact. We apply our formulation to benchmark simulated annealing on a class of maximum-2-satisfiability (MAX2SAT) problems. We also compare the performance of a D-Wave 2X quantum annealer to the Hamze-Freitas-Selby (HFS) solver, a specialized classical heuristic algorithm designed for low-tree-width graphs. On a set of frustrated-loop instances with planted solutions defined on up to N =1098 variables, the D-Wave device is 2 orders of magnitude faster than the HFS solver, and, modulo known caveats related to suboptimal annealing times, exhibits identical scaling with problem size.
Optimal search strategies on complex multi-linked networks
Di Patti, Francesca; Fanelli, Duccio; Piazza, Francesco
2015-01-01
In this paper we consider the problem of optimal search strategies on multi-linked networks, i.e. graphs whose nodes are endowed with several independent sets of links. We focus preliminarily on agents randomly hopping along the links of a graph, with the additional possibility of performing non-local hops to randomly chosen nodes with a given probability. We show that an optimal combination of the two jump rules exists that maximises the efficiency of target search, the optimum reflecting the topology of the network. We then generalize our results to multi-linked networks with an arbitrary number of mutually interfering link sets. PMID:25950716
ERIC Educational Resources Information Center
Naylor, Mary; Keating, Stacen A.
2008-01-01
Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…
ERIC Educational Resources Information Center
Naylor, Mary; Keating, Stacen A.
2008-01-01
Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…
Optimal domain decomposition strategies
NASA Technical Reports Server (NTRS)
Yoon, Yonghyun; Soni, Bharat K.
1995-01-01
The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.
2014-09-11
This image, taken by NASA Mars Reconnaissance Orbiter, shows the transition between the Murray Formation, in which layers are poorly expressed and difficult to trace from orbit, and the hematite ridge, which is made up of continuous layers.
Structural transitions in clusters.
Hartke, Bernd
2002-05-03
If one adds more particles to a cluster, the energetically optimal structure is neither preserved nor does it change in a continuous fashion. Instead, one finds several cluster size regions where one structural principle dominates almost without exception, and rather narrow boundary regions in-between. The structure of the solid is usually reached only at relatively large sizes, after more than one structural transition. The occurrence of this general phenomenon of size-dependent structural transitions does not seem to depend on the nature of the particles, it is found for atomic, molecular, homogeneous, and heterogeneous clusters alike. Clearly, it is a collective many-body phenomenon which can in principle be calculated but not understood in a fully reductionistic manner. Actual calculations with sufficient accuracy are not feasible today, because of the enormous computational expense, even when unconventional evolutionary algorithms are employed for global geometry optimization. Therefore, simple rules for cluster structures are highly desirable. In fact, we are dealing here not just with the academic quest for linkages between cluster structure and features of the potential energy surface, but structural transitions in clusters are also of immediate relevance for many natural and industrial processes, ranging from crystal growth all the way to nanotechnology. This article provides an exemplary overview of research on this topic, from simple model systems where first qualitative explanations start to be successful, up to more realistic complex systems which are still beyond our understanding.
Research in bus and rail transit operations
Chatterjee, A.; Wegmann, F.J.; Ceder, A.; Levinson, H.S.; Hollander, A.
1989-01-01
The 10 papers in the report deal with the following areas: Private Sector Involvement in Sponsoring Sunday Bus Service; Optimal Design of Transit Short-Turn Trips; New York City's Unfranchised Buses: Case Study in Deregulation; Critical Factors in Planning Multimodal Passenger Terminals; Use of Travelers' Attitudes in Rail Service Design; Driven, Attended, and Fully Automated Transit; Qualitative Comparison; Impact on Transit Patronage of Cessation or Inauguration of Rail Service; Use of Productivity Factors in Estimating LRT Operating Costs; Simulation Study To Evaluate Spare Ratios in Bus Transit Systems; Statistical Evaluation of Spare Ratio in Transit Rolling Stock.
NASA Astrophysics Data System (ADS)
Alcock-Zeilinger, J.; Weigert, H.
2017-05-01
In this paper, we give a generic algorithm of the transition operators between Hermitian Young projection operators corresponding to equivalent irreducible representations of 𝖲𝖴 (N ) , using the compact expressions of Hermitian Young projection operators derived in the work of Alcock-Zeilinger and Weigert [eprint arXiv:1610.10088 [math-ph
2006-06-09
Podesta for the Heads of Executive Departments and Agencies, “Presidential Transition Guidance,” Nov. 13, 2000. 89 U.S. General Services Administration...2000, presidential election, White House Chief of Staff John Podesta issued a November 13, 2000, memorandum to executive branch agencies stating that
ERIC Educational Resources Information Center
Cassidy, Joan
1998-01-01
Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)
2012-06-05
Leslie Lowes from the NASA Jet Propulsion Laboratory in Pasadena, Calif., views the June 5, 2012, Venus transit through a solar telescope. Lowes participated in an education workshop at the INFINITY at NASA Stennis Space Center visitor center and joined others to view the rare celestial event when Venus traverses the face of the sun.
2012-06-05
Guests at the INFINITY at NASA Stennis Space Center visitor center use special solar sunglasses to catch a lifetime view of the Venus transit June 5, 2012. The rare celestial event in which the planet Venus traverses the face of the sun will not be visible from Earth again until 2117.
ERIC Educational Resources Information Center
Kofoed, Jette
2008-01-01
This analysis concentrates on the case of a child, Jenny. The paper suggests that the concept of liminality may hold the key to an understanding of muted subject positions like the one assumed by Jenny in a school class. Liminality is proposed as a way of conceptualizing transitions where the subject in question transgresses established rules and…
ERIC Educational Resources Information Center
Cassidy, Joan
1998-01-01
Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)
ERIC Educational Resources Information Center
Gallick, Barb; Lee, Lisa
2010-01-01
Adults often find themselves transitioning from one activity to another in a short time span. Most of the time, they do not feel they have a lot of control over their schedules, but wish that they could carve out extended time to relax and focus on one project. Picture a group of children in the block area who have spent 15 or 20 minutes building…
2012-06-05
A "transit of Venus" occurs when the planet Venus passes directly between the sun and the Earth. During the event, Venus will be seen from Earth as a small black sphere moving across the face of the sun. Such an event won’t occur again until the year 2117. The Goddard Visitor Center hosted a watch party that included near real-time images from NASA’s Solar Dynamics Observatory mission, coverage of the event from several locations via NASA TV, in-person presentations by NASA experts, hands-on activities for children of all ages. Heavy cloud cover did not allow viewing opportunities of the transit via solar telescopes. Credit: NASA/Goddard Space Flight Center/Bill Hrybyk NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
NASA Technical Reports Server (NTRS)
Laird, Philip
1992-01-01
We distinguish static and dynamic optimization of programs: whereas static optimization modifies a program before runtime and is based only on its syntactical structure, dynamic optimization is based on the statistical properties of the input source and examples of program execution. Explanation-based generalization is a commonly used dynamic optimization method, but its effectiveness as a speedup-learning method is limited, in part because it fails to separate the learning process from the program transformation process. This paper describes a dynamic optimization technique called a learn-optimize cycle that first uses a learning element to uncover predictable patterns in the program execution and then uses an optimization algorithm to map these patterns into beneficial transformations. The technique has been used successfully for dynamic optimization of pure Prolog.
NASA Technical Reports Server (NTRS)
2006-01-01
22 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a transition from one of the many layered troughs in the north polar region of Mars to the relatively homogeneous-looking upper surface of the polar cap. The difference in brightness across this scene is a function of several factors, one of which is the amount of dust versus that of ice in any given location. The bright material that dominates the scene is largely water ice.
Location near: 83.2oN, 297.8oW Image width: 3 km (1.9 mi) Illumination from: lower right Season: Northern Summer
ERIC Educational Resources Information Center
Letyagin, Alexander
2015-01-01
The article deals with the problems of content and technological modernization that arise in the process of transition from the information paradigm of education to the activity one. A combined training model of class teaching using information, practice-based activity and visual components is offered as an example and a result of innovative…
Edge orientation for optimizing controllability of complex networks
NASA Astrophysics Data System (ADS)
Xiao, Yan-Dong; Lao, Song-Yang; Hou, Lv-Lin; Bai, Liang
2014-10-01
Recently, as the controllability of complex networks attracts much attention, how to design and optimize the controllability of networks has become a common and urgent problem in the field of controlling complex networks. Previous work focused on the structural perturbation and neglected the role of edge direction to optimize the network controllability. In a recent work [Phys. Rev. Lett. 103, 228702 (2009), 10.1103/PhysRevLett.103.228702], the authors proposed a simple method to enhance the synchronizability of networks by assignment of link direction while keeping network topology unchanged. However, the controllability is fundamentally different from synchronization. In this work, we systematically propose the definition of assigning direction to optimize controllability, which is called the edge orientation for optimal controllability problem (EOOC). To solve the EOOC problem, we construct a switching network and transfer the EOOC problem to find the maximum independent set of the switching network. We prove that the principle of our optimization method meets the sense of unambiguity and optimum simultaneously. Furthermore, the relationship between the degree-degree correlations and EOOC are investigated by experiments. The results show that the disassortativity pattern could weaken the orientation for optimal controllability, while the assortativity pattern has no correlation with EOOC. All the experimental results of this work verify that the network structure determines the network controllability and the optimization effects.
2015-07-06
optimization solvers, they typically exhibit extremely poor performance . We develop a variety of effective model and algorithm enhancement techniques...commercial optimization solvers, they typically exhibit extremely poor performance . We develop a variety of effective model and algorithm enhancement ...class of problems, and developed strengthened formulations and algorithmic techniques which perform significantly better than standard MIP
Carver, Charles S; Scheier, Michael F
2014-06-01
Optimism is a cognitive construct (expectancies regarding future outcomes) that also relates to motivation: optimistic people exert effort, whereas pessimistic people disengage from effort. Study of optimism began largely in health contexts, finding positive associations between optimism and markers of better psychological and physical health. Physical health effects likely occur through differences in both health-promoting behaviors and physiological concomitants of coping. Recently, the scientific study of optimism has extended to the realm of social relations: new evidence indicates that optimists have better social connections, partly because they work harder at them. In this review, we examine the myriad ways this trait can benefit an individual, and our current understanding of the biological basis of optimism. Copyright © 2014 Elsevier Ltd. All rights reserved.
Carver, Charles S.; Scheier, Michael F.
2014-01-01
Optimism is a cognitive construct (expectancies regarding future outcomes) that also relates to motivation: optimistic people exert effort, whereas pessimistic people disengage from effort. Study of optimism began largely in health contexts, finding positive associations between optimism and markers of better psychological and physical health. Physical health effects likely occur through differences in both health-promoting behaviors and physiological concomitants of coping. Recently, the scientific study of optimism has extended to the realm of social relations: new evidence indicates that optimists have better social connections, partly because they work harder at them. In this review, we examine the myriad ways this trait can benefit an individual, and our current understanding of the biological basis of optimism. PMID:24630971
Transitions: A Personal Perspective.
ERIC Educational Resources Information Center
Wood, Ann Stace
1995-01-01
Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)
Topological Lifshitz transitions
NASA Astrophysics Data System (ADS)
Volovik, G. E.
2017-01-01
Different types of Lifshitz transitions are governed by topology in momentum space. They involve the topological transitions with the change of topology of Fermi surfaces, Weyl and Dirac points, nodal lines, and also the transitions between the fully gapped states.
... Centers Workspaces Workspaces Who Knows What? Survey Item Bank Search for: Transition to Adulthood Link-checked, June ... reading… Back to top IDEA’s Definition of Transition Services Any discussion of transition services must begin with ...
OPTIMIZING THROUGH CO-EVOLUTIONARY AVALANCHES
S. BOETTCHER; A. PERCUS
2000-08-01
We explore a new general-purpose heuristic for finding high-quality solutions to hard optimization problems. The method, called extremal optimization, is inspired by ''self-organized critically,'' a concept introduced to describe emergent complexity in many physical systems. In contrast to Genetic Algorithms which operate on an entire ''gene-pool'' of possible solutions, extremal optimization successively replaces extremely undesirable elements of a sub-optimal solution with new, random ones. Large fluctuations, called ''avalanches,'' ensue that efficiently explore many local optima. Drawing upon models used to simulate far-from-equilibrium dynamics, extremal optimization complements approximation methods inspired by equilibrium statistical physics, such as simulated annealing. With only one adjustable parameter, its performance has proved competitive with more elaborate methods, especially near phase transitions. Those phase transitions are found in the parameter space of most optimization problems, and have recently been conjectured to be the origin of some of the hardest instances in computational complexity. We will demonstrate how extremal optimization can be implemented for a variety of combinatorial optimization problems. We believe that extremal optimization will be a useful tool in the investigation of phase transitions in combinatorial optimization problems, hence valuable in elucidating the origin of computational complexity.
Nonconvex optimization and jamming
NASA Astrophysics Data System (ADS)
Kallus, Yoav
Recent work on the jamming transition of particles with short-range interactions has drawn connections with models based on minimization problems with linear inequality constraints and a concave objective. These properties reduce the continuous optimization problem to a discrete search among the corners of the feasible polytope. I will discuss results from simulations of models with and without quenched disorder, exhibiting critical power laws, scaling collapse, and protocol dependence. These models are also well-suited for study using tools of algebraic topology, which I will discuss briefly. Supported by an Omidyar Fellowship at the Santa Fe Institute.
On the Bellman's principle of optimality
NASA Astrophysics Data System (ADS)
Gross, Eitan
2016-11-01
Bellman's equation is widely used in solving stochastic optimal control problems in a variety of applications including investment planning, scheduling problems and routing problems. Building on Markov decision processes for stationary policies, we present a new proof for Bellman's equation of optimality. Our proof rests its case on the availability of an explicit model of the environment that embodies transition probabilities and associated costs.
NASA Astrophysics Data System (ADS)
Kekalo, I. B.; Mogil'nikov, P. S.
2016-07-01
The influence of the holding time upon annealing on the temperature of the viscous-brittle transition (temperature of embrittlement) T f in a cobalt-based amorphous alloy of the composition Co69Fe3.7Cr3.8Si12.5B11 with a very low saturation magnetostriction λs (<10-7) has been studied. It has been established that the dependence of the embrittlement temperature T f on the of time of holding t a can be described by an Arrhenius equation and that the embrittlement at the annealing temperatures above and below 300°C is described by different kinetic parameters. In the alloy under study, irrespective of the holding time, embrittlement occurs in a very narrow range of annealing temperatures, which does not exceed 5 K. Based on the experimental data on the evolution of the hysteresis magnetic properties upon the isochronous annealings and upon the isothermal holding, the regime of heat treatment that ensures a very high (about 50000) magnitude of the permeability µ5 ( H = 5 mOe, f = 1 kHz) without the transition of the alloy into a brittle state has been determined.
Optimality in neuromuscular systems.
Theodorou, Evangelos; Valero-Cuevas, Francisco J
2010-01-01
We provide an overview of optimal control methods to nonlinear neuromuscular systems and discuss their limitations. Moreover we extend current optimal control methods to their application to neuromuscular models with realistically numerous musculotendons; as most prior work is limited to torque-driven systems. Recent work on computational motor control has explored the used of control theory and estimation as a conceptual tool to understand the underlying computational principles of neuromuscular systems. After all, successful biological systems regularly meet conditions for stability, robustness and performance for multiple classes of complex tasks. Among a variety of proposed control theory frameworks to explain this, stochastic optimal control has become a dominant framework to the point of being a standard computational technique to reproduce kinematic trajectories of reaching movements (see [12]) In particular, we demonstrate the application of optimal control to a neuromuscular model of the index finger with all seven musculotendons producing a tapping task. Our simulations include 1) a muscle model that includes force- length and force-velocity characteristics; 2) an anatomically plausible biomechanical model of the index finger that includes a tendinous network for the extensor mechanism and 3) a contact model that is based on a nonlinear spring-damper attached at the end effector of the index finger. We demonstrate that it is feasible to apply optimal control to systems with realistically large state vectors and conclude that, while optimal control is an adequate formalism to create computational models of neuro-musculoskeletal systems, there remain important challenges and limitations that need to be considered and overcome such as contact transitions, curse of dimensionality, and constraints on states and controls.
NASA Technical Reports Server (NTRS)
Macready, William; Wolpert, David
2005-01-01
We demonstrate a new framework for analyzing and controlling distributed systems, by solving constrained optimization problems with an algorithm based on that framework. The framework is ar. information-theoretic extension of conventional full-rationality game theory to allow bounded rational agents. The associated optimization algorithm is a game in which agents control the variables of the optimization problem. They do this by jointly minimizing a Lagrangian of (the probability distribution of) their joint state. The updating of the Lagrange parameters in that Lagrangian is a form of automated annealing, one that focuses the multi-agent system on the optimal pure strategy. We present computer experiments for the k-sat constraint satisfaction problem and for unconstrained minimization of NK functions.
Radionuclide transit in esophageal varices
Yeh, S.H.; Wang, S.J.; Wu, L.C.; Liu, R.S.; Tsai, Y.T.; Chiang, T.T.
1985-05-01
This study assessed esophageal motility in patients with esophageal varices by radionuclide transit studies. Data were acquired in list mode after an oral dose of 0.5 mCi Tc-99m sulfur colloid in 10 ml of water in the supine position above a low-energy all-purpose collimator of a gamma camera. The condensed image (CI) superimposed with a centroid curve was also produced in each case. Twenty-five normal subjects (N) and 32 patients (pts) with esophageal varices by endoscopy (large varices in Grades IV and V in 8 and small varices in Grade III or less in 24) were studied. TMTT, RTT, RF, and RI were all significantly increased in pts as compared to N. Especially, the transit time for the middle third (6.7 +- 2.6 sec vs 3.5 +- 0.9 sec in N, rho < 0.005) had the optimal sensitivy and specificity of 88% each at the cutoff value of 4.2 sec as determined by ROC analysis. In summary, radionuclide transit disorders occur in the majority of pts with esopageal varices. The middle RTT and CI are both optimal in sensitivity and specificity for detecting the abnormalities.
ERIC Educational Resources Information Center
Kellems, Ryan, Comp.; Morningstar, Mary E., Comp.
2009-01-01
The Tips for Transition contains 134 Transition Tips submitted from all over the country by practitioners. The purpose of the Tips was to identify grassroots transition practices being used by practitioners. Tips are categorized into the following domains: (1) Transition Planning; (2) Student Involvement; (3) Family Involvement; (4) Curriculum and…
Optimal Protocols and Optimal Transport in Stochastic Thermodynamics
NASA Astrophysics Data System (ADS)
Aurell, Erik; Mejía-Monasterio, Carlos; Muratore-Ginanneschi, Paolo
2011-06-01
Thermodynamics of small systems has become an important field of statistical physics. Such systems are driven out of equilibrium by a control, and the question is naturally posed how such a control can be optimized. We show that optimization problems in small system thermodynamics are solved by (deterministic) optimal transport, for which very efficient numerical methods have been developed, and of which there are applications in cosmology, fluid mechanics, logistics, and many other fields. We show, in particular, that minimizing expected heat released or work done during a nonequilibrium transition in finite time is solved by the Burgers equation and mass transport by the Burgers velocity field. Our contribution hence considerably extends the range of solvable optimization problems in small system thermodynamics.
Sejnowski, Terrence J.; Poizner, Howard; Lynch, Gary; Gepshtein, Sergei; Greenspan, Ralph J.
2014-01-01
Human performance approaches that of an ideal observer and optimal actor in some perceptual and motor tasks. These optimal abilities depend on the capacity of the cerebral cortex to store an immense amount of information and to flexibly make rapid decisions. However, behavior only approaches these limits after a long period of learning while the cerebral cortex interacts with the basal ganglia, an ancient part of the vertebrate brain that is responsible for learning sequences of actions directed toward achieving goals. Progress has been made in understanding the algorithms used by the brain during reinforcement learning, which is an online approximation of dynamic programming. Humans also make plans that depend on past experience by simulating different scenarios, which is called prospective optimization. The same brain structures in the cortex and basal ganglia that are active online during optimal behavior are also active offline during prospective optimization. The emergence of general principles and algorithms for goal-directed behavior has consequences for the development of autonomous devices in engineering applications. PMID:25328167
Sejnowski, Terrence J; Poizner, Howard; Lynch, Gary; Gepshtein, Sergei; Greenspan, Ralph J
2014-05-01
Human performance approaches that of an ideal observer and optimal actor in some perceptual and motor tasks. These optimal abilities depend on the capacity of the cerebral cortex to store an immense amount of information and to flexibly make rapid decisions. However, behavior only approaches these limits after a long period of learning while the cerebral cortex interacts with the basal ganglia, an ancient part of the vertebrate brain that is responsible for learning sequences of actions directed toward achieving goals. Progress has been made in understanding the algorithms used by the brain during reinforcement learning, which is an online approximation of dynamic programming. Humans also make plans that depend on past experience by simulating different scenarios, which is called prospective optimization. The same brain structures in the cortex and basal ganglia that are active online during optimal behavior are also active offline during prospective optimization. The emergence of general principles and algorithms for goal-directed behavior has consequences for the development of autonomous devices in engineering applications.
Lee, John R.
1975-01-01
Optimal fluoridation has been defined as that fluoride exposure which confers maximal cariostasis with minimal toxicity and its values have been previously determined to be 0.5 to 1 mg per day for infants and 1 to 1.5 mg per day for an average child. Total fluoride ingestion and urine excretion were studied in Marin County, California, children in 1973 before municipal water fluoridation. Results showed fluoride exposure to be higher than anticipated and fulfilled previously accepted criteria for optimal fluoridation. Present and future water fluoridation plans need to be reevaluated in light of total environmental fluoride exposure. PMID:1130041
1994-01-01
AD-A277 644 ARAI !: ’ Mesh Optimization Technical Report # 93-01-01 Hughes Hoppe, Tony DeRose, Tom Duchamp , John McDonald and Werner Stuetzle DTIC...SrECT3D I 94 i 31 108 Mesh Optimization Technical Report # 93-01-01 Hughes Hoppe, Tony DeRose, Tom Duchamp , John McDonald and Werner Stuetzle Department...1:1. Januairy 1991. [2] T. DeRose. 11. Hoppe, T. Duchamp . .1. McDonald. and NV. Stuetzle. Fitting of surfaces to scattered data. ,PIE, 1830:212-220
Transiting Exoplanet Observations at Grinnell College
NASA Astrophysics Data System (ADS)
Sauerhaft, Julia; Slough, P.; Cale, B.; Kempton, E.
2014-01-01
Grinnell College, a small liberal arts college in Grinnell, Iowa with 1600 undergraduate students, is home to the Grant O. Gale Observatory. Over the past year, we have successfully detected extrasolar planets using the transit method with our 24-inch Cassegrain reflecting telescope equipped with a CCD camera. With little light pollution and an easily accessible observatory, Grinnell College is an optimal location for transiting exoplanet observations. With the current telescope set-up and CCD camera, we have taken time series data and created image calibration and post-processing programs that detect exoplanet transits at high photometric precision. In the future, we will continue to use these observation and data reduction procedures to conduct transiting exoplanet research. Goals for our research program include performing follow-up observations of transiting exoplanet candidates to confirm their planetary nature, searching for additional exoplanets in known planetary systems using the transit timing detection method, tracking long period transiting planets, and refining properties of exoplanets and their host stars. Ground-based transiting planet science is especially important in the post-Kepler era, and our dedicated mid-sized telescope with plenty of access to dark clear nights provides an ideal resource for a variety of follow up and exoplanet detection efforts.
Optimal back-to-front airplane boarding.
Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran
2013-06-01
The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.
Partners in Transition: Preparing Transition Specialists.
ERIC Educational Resources Information Center
Sample, Pat; And Others
Colorado rural special educators are experiencing tremendous challenges in providing mandated transition services to students with special needs. The School of Education and the Department of Occupational Therapy at Colorado State University have developed a program to create rural transition specialists through preservice and inservice training…
Gas turbine combustor transition
Coslow, B.J.; Whidden, G.L.
1999-05-25
A method is described for converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit. 7 figs.
Gas turbine combustor transition
Coslow, Billy Joe; Whidden, Graydon Lane
1999-01-01
A method of converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit.
NASA Technical Reports Server (NTRS)
Vanderplaats, G. N.; Chen, Xiang; Zhang, Ning-Tian
1988-01-01
The use of formal numerical optimization methods for the design of gears is investigated. To achieve this, computer codes were developed for the analysis of spur gears and spiral bevel gears. These codes calculate the life, dynamic load, bending strength, surface durability, gear weight and size, and various geometric parameters. It is necessary to calculate all such important responses because they all represent competing requirements in the design process. The codes developed here were written in subroutine form and coupled to the COPES/ADS general purpose optimization program. This code allows the user to define the optimization problem at the time of program execution. Typical design variables include face width, number of teeth and diametral pitch. The user is free to choose any calculated response as the design objective to minimize or maximize and may impose lower and upper bounds on any calculated responses. Typical examples include life maximization with limits on dynamic load, stress, weight, etc. or minimization of weight subject to limits on life, dynamic load, etc. The research codes were written in modular form for easy expansion and so that they could be combined to create a multiple reduction optimization capability in future.
Optimization by record dynamics
NASA Astrophysics Data System (ADS)
Barettin, Daniele; Sibani, Paolo
2014-03-01
Large dynamical changes in thermalizing glassy systems are triggered by trajectories crossing record sized barriers, a behavior revealing the presence of a hierarchical structure in configuration space. The observation is here turned into a novel local search optimization algorithm dubbed record dynamics optimization, or RDO. RDO uses the Metropolis rule to accept or reject candidate solutions depending on the value of a parameter akin to the temperature and minimizes the cost function of the problem at hand through cycles where its ‘temperature’ is raised and subsequently decreased in order to expediently generate record high (and low) values of the cost function. Below, RDO is introduced and then tested by searching for the ground state of the Edwards-Anderson spin-glass model, in two and three spatial dimensions. A popular and highly efficient optimization algorithm, parallel tempering (PT), is applied to the same problem as a benchmark. RDO and PT turn out to produce solutions of similar quality for similar numerical effort, but RDO is simpler to program and additionally yields geometrical information on the system’s configuration space which is of interest in many applications. In particular, the effectiveness of RDO strongly indicates the presence of the above mentioned hierarchically organized configuration space, with metastable regions indexed by the cost (or energy) of the transition states connecting them.
Biocapacity optimization in regional planning
Guo, Jianjun; Yue, Dongxia; Li, Kai; Hui, Cang
2017-01-01
Ecological overshoot has been accelerating across the globe. Optimizing biocapacity has become a key to resolve the overshoot of ecological demand in regional sustainable development. However, most literature has focused on reducing ecological footprint but ignores the potential of spatial optimization of biocapacity through regional planning of land use. Here we develop a spatial probability model and present four scenarios for optimizing biocapacity of a river basin in Northwest China. The potential of enhanced biocapacity and its effects on ecological overshoot and water consumption in the region were explored. Two scenarios with no restrictions on croplands and water use reduced the overshoot by 29 to 53%, and another two scenarios which do not allow croplands and water use to increase worsened the overshoot by 11 to 15%. More spatially flexible transition rules of land use led to higher magnitude of change after optimization. However, biocapacity optimization required a large amount of additional water resources, casting considerable pressure on the already water-scarce socio-ecological system. Our results highlight the potential for policy makers to manage/optimize regional land use which addresses ecological overshoot. Investigation on the feasibility of such spatial optimization complies with the forward-looking policies for sustainable development and deserves further attention. PMID:28112224
Biocapacity optimization in regional planning
NASA Astrophysics Data System (ADS)
Guo, Jianjun; Yue, Dongxia; Li, Kai; Hui, Cang
2017-01-01
Ecological overshoot has been accelerating across the globe. Optimizing biocapacity has become a key to resolve the overshoot of ecological demand in regional sustainable development. However, most literature has focused on reducing ecological footprint but ignores the potential of spatial optimization of biocapacity through regional planning of land use. Here we develop a spatial probability model and present four scenarios for optimizing biocapacity of a river basin in Northwest China. The potential of enhanced biocapacity and its effects on ecological overshoot and water consumption in the region were explored. Two scenarios with no restrictions on croplands and water use reduced the overshoot by 29 to 53%, and another two scenarios which do not allow croplands and water use to increase worsened the overshoot by 11 to 15%. More spatially flexible transition rules of land use led to higher magnitude of change after optimization. However, biocapacity optimization required a large amount of additional water resources, casting considerable pressure on the already water-scarce socio-ecological system. Our results highlight the potential for policy makers to manage/optimize regional land use which addresses ecological overshoot. Investigation on the feasibility of such spatial optimization complies with the forward-looking policies for sustainable development and deserves further attention.
Biocapacity optimization in regional planning.
Guo, Jianjun; Yue, Dongxia; Li, Kai; Hui, Cang
2017-01-23
Ecological overshoot has been accelerating across the globe. Optimizing biocapacity has become a key to resolve the overshoot of ecological demand in regional sustainable development. However, most literature has focused on reducing ecological footprint but ignores the potential of spatial optimization of biocapacity through regional planning of land use. Here we develop a spatial probability model and present four scenarios for optimizing biocapacity of a river basin in Northwest China. The potential of enhanced biocapacity and its effects on ecological overshoot and water consumption in the region were explored. Two scenarios with no restrictions on croplands and water use reduced the overshoot by 29 to 53%, and another two scenarios which do not allow croplands and water use to increase worsened the overshoot by 11 to 15%. More spatially flexible transition rules of land use led to higher magnitude of change after optimization. However, biocapacity optimization required a large amount of additional water resources, casting considerable pressure on the already water-scarce socio-ecological system. Our results highlight the potential for policy makers to manage/optimize regional land use which addresses ecological overshoot. Investigation on the feasibility of such spatial optimization complies with the forward-looking policies for sustainable development and deserves further attention.
Optimal Search and Interdiction Planning
2014-06-18
use (United Nations Office on Drugs and Crime , 2012, p. 1) and over 1,500 metric tons of illegal drugs are seized in transit to United States annually...Naval Research, Mathe - matical Optimization and Operations Research Program. References Alpern, S., Gal, S., 2003. The Theory of Search Games and...and Crime , 2012. World Drug Report. United Nations, New York, NY. US Department of Justice, 2014. National Drug Threat Assessment. Retrieved June 3
Optimal protocols for slowly driven quantum systems
NASA Astrophysics Data System (ADS)
Zulkowski, Patrick R.; DeWeese, Michael R.
2015-09-01
The design of efficient quantum information processing will rely on optimal nonequilibrium transitions of driven quantum systems. Building on a recently developed geometric framework for computing optimal protocols for classical systems driven in finite time, we construct a general framework for optimizing the average information entropy for driven quantum systems. Geodesics on the parameter manifold endowed with a positive semidefinite metric correspond to protocols that minimize the average information entropy production in finite time. We use this framework to explicitly compute the optimal entropy production for a simple two-state quantum system coupled to a heat bath of bosonic oscillators, which has applications to quantum annealing.
Conceptualizing Transitions to Adulthood
ERIC Educational Resources Information Center
Wyn, Johanna
2014-01-01
This chapter provides an overview of theories of the transition to young adulthood. It sets out the argument for conceptual renewal and discusses some implications of new patterns of transition for adult education.
Conceptualizing Transitions to Adulthood
ERIC Educational Resources Information Center
Wyn, Johanna
2014-01-01
This chapter provides an overview of theories of the transition to young adulthood. It sets out the argument for conceptual renewal and discusses some implications of new patterns of transition for adult education.
ERIC Educational Resources Information Center
Kneeland, Steven J.
1980-01-01
Having identified the problem of managerial transition in a previous article (CE 510 277), the author outlines a strategy for change which includes performance appraisal, definition of the management structure, and counselling for the individual in transition. (SK)
Psychologists and the transition from pediatrics to adult healthcare
Gray, Wendy N.; Monaghan, Maureen C.; Marchak, Jordan Gilleland; Driscoll, Kimberly A.; Hilliard, Marisa E.
2015-01-01
Purpose Guidelines for optimal transition call for multidisciplinary teams, including psychologists, to address youth and young adults’ multifactorial needs. This study aimed to characterize psychologists’ roles in and barriers to involvement in transition from pediatric to adult healthcare. Methods Psychologists were invited via professional listservs to complete an online survey about practice settings, roles in transition programming, barriers to involvement, and funding sources. Participants also responded to open-ended questions about their experiences in transition programs. Results One hundred participants responded to the survey. Involvement in transition was reported at multiple levels from individual patient care to institutional transition programming, and 65% reported more than one level of involvement. Direct clinical care (88%), transition-related research (50%) and/or leadership (44%) involvement were reported, with 59% reporting more than one role. Respondents often described advocating for their involvement on transition teams. Various sources of funding were reported, yet 23% reported no funding for their work. Barriers to work in transition were common and included healthcare systems issues such as poor coordination among providers or lack of a clear transition plan within the clinic/institution. Conclusions Psychologists assume numerous roles in the transition of adolescents from pediatric to adult healthcare. With training in healthcare transition-related issues, psychologists are ideally positioned to partner with other health professionals to develop and implement transition programs in multi-disciplinary settings, provided healthcare system barriers can be overcome. PMID:26499856
Psychologists and the Transition From Pediatrics to Adult Health Care.
Gray, Wendy N; Monaghan, Maureen C; Gilleland Marchak, Jordan; Driscoll, Kimberly A; Hilliard, Marisa E
2015-11-01
Guidelines for optimal transition call for multidisciplinary teams, including psychologists, to address youth and young adults' multifactorial needs. This study aimed to characterize psychologists' roles in and barriers to involvement in transition from pediatric to adult health care. Psychologists were invited via professional listservs to complete an online survey about practice settings, roles in transition programming, barriers to involvement, and funding sources. Participants also responded to open-ended questions about their experiences in transition programs. One hundred participants responded to the survey. Involvement in transition was reported at multiple levels from individual patient care to institutional transition programming, and 65% reported more than one level of involvement. Direct clinical care (88%), transition-related research (50%), and/or leadership (44%) involvement were reported, with 59% reporting more than one role. Respondents often described advocating for their involvement on transition teams. Various sources of funding were reported, yet, 23% reported no funding for their work. Barriers to work in transition were common and included health care systems issues such as poor coordination among providers or lack of a clear transition plan within the clinic/institution. Psychologists assume numerous roles in the transition of adolescents from pediatric to adult health care. With training in health care transition-related issues, psychologists are ideally positioned to partner with other health professionals to develop and implement transition programs in multidisciplinary settings, provided health care system barriers can be overcome. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.
NASA Technical Reports Server (NTRS)
1985-01-01
The concept of a large disturbance bypass mechanism for the initiation of transition is reviewed and studied. This mechanism, or some manifestation thereof, is suspected to be at work in the boundary layers present in a turbine flow passage. Discussion is presented on four relevant subtopics: (1) the effect of upstream disturbances and wakes on transition; (2) transition prediction models, code development, and verification; (3) transition and turbulence measurement techniques; and (4) the hydrodynamic condition of low Reynolds number boundary layers.
Cosmological phase transitions
Kolb, E.W. |
1993-10-01
If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.
Multidisciplinary optimization
Dennis, J.; Lewis, R.M.; Cramer, E.J.; Frank, P.M.; Shubin, G.R.
1994-12-31
This talk will use aeroelastic design and reservoir characterization as examples to introduce some approaches to MDO, or Multidisciplinary Optimization. This problem arises especially in engineering design, where it is considered of paramount importance in today`s competitive global business climate. It is interesting to an optimizer because the constraints involve coupled dissimilar systems of parameterized partial differential equations each arising from a different discipline, like structural analysis, computational fluid dynamics, etc. Usually, these constraints are accessible only through pde solvers rather than through algebraic residual calculations as we are used to having. Thus, just finding a multidisciplinary feasible point is a daunting task. Many such problems have discrete variable disciplines, multiple objectives, and other challenging features. After discussing some interesting practical features of the design problem, we will give some standard ways to formulate the problem as well as some novel ways that lend themselves to divide-and-conquer parallelism.
ERIC Educational Resources Information Center
Wallace, Teri, Ed.; And Others
1992-01-01
This feature issue of a quarterly bulletin on community integration addresses the topic of transition services for preparing youth with disabilities for adult community living. It contains articles with the following titles and authors: "Transition: The Next Five Years" (David R. Johnson and others); "Transition Policy in the 1990s:…
Transition: Preschool to Kindergarten
ERIC Educational Resources Information Center
Arizona Department of Education, 2007
2007-01-01
Transition is movement or change without interruption. It should be a smooth flow from one place or condition to another. While the transition plan for a student receiving special education services is designed to prepare him or her for life after high school, transition can start when a child enters preschool. The second of six distinct stages of…
1992-12-01
steady-state fluid flow through porous media. Some of these problems can be formulated as a variational inequality af- ter an ingenious transformation...constrai- ned optimization problems, we describe two new solution methods which re- sulted from the research. The first is a continuous "inexact...34 method for sol- ving systems of nonlinear equations and complementarity problems (along the lines of the DAFNE Method), and the second is a continuous
The Transition to Secondary Progressive Multiple Sclerosis
Wood, Fiona; Brain, Katherine E.; Edwards, Michelle; Jones, Rhiannon; Wallbank, Rachel; Robertson, Neil P.; Edwards, Adrian
2016-01-01
Background: Identifying the transition from relapsing-remitting to secondary progressive multiple sclerosis (SPMS) can be challenging for clinicians. Little previous research has explored how professionals experience working with patients during this specific stage of the disease. We explored the experiences of a group of multidisciplinary professionals who support patients in the transition to SPMS to describe this stage from a professional perspective. Methods: This qualitative semistructured interview study included 11 professionals (medical, nursing, and allied health professionals; specialists and generalists) working with patients with MS in South Wales, United Kingdom. Thematic analysis of the interview data was performed. Results: Two overarching themes were identified: the transition and providing support. The transition theme comprised issues related to recognizing and communicating about SPMS. Uncertainty influenced recognizing the transition and knowing how to discuss it with patients. The providing support theme included descriptions of challenging aspects of patient care, providing support for caregivers, using the multidisciplinary team, and working within service constraints. Providing adequate psychological support and engaging patients with self-management approaches were seen as particularly challenging. Conclusions: Caring for patients in the transition to SPMS generates specific challenges for professionals. Further research on health-care interactions and patients'/professionals' experiences regarding the transition phase may help identify strategies for professional development and learning and how to optimize the patient experience at this difficult stage of disease. PMID:27803641
Dementia, medication and transitions of care.
Deeks, Louise S; Cooper, Gabrielle M; Draper, Brian; Kurrle, Susan; Gibson, Diane M
2016-01-01
Persons with dementia (PWD) often have complex medication regimens and are at risk of medication problems during the multiple transitions of care experienced as the condition progresses. To explore medication processes in acute care episodes and care transitions for PWD and to make recommendations to improve practice. Semi-structured interviews were conducted by two pharmacy researchers from a focused purposive sample of fifty-one participants (carers, health professionals, Alzheimer's Australia staff) from urban and rural Australia. After written consent, the interviews were audio-recorded then transcribed verbatim for face-to-face interviews, or notes were taken during the interview if conducted by telephone. The transcripts were checked for accuracy by the pharmacy researchers. Thematic analysis of the data was undertaken independently by the two researchers to reduce bias and any disagreements were resolved by discussion. Themes identified were: medication reconciliation; no modified planning for care transitions; underutilization of information technology; multiple prescribers; residential aged care facilities; and medication reviews by pharmacists. Sub themes were: access to appropriate staff; identification of dementia; dose administration aids; and staff training. Medication management is sub-optimal for PWD during care transitions and may compromise safety. Suggested improvements included: increased involvement of pharmacists in care transitions; outreach or transitional health care professionals; modified planning for care transitions for individuals over 80 years; co-ordinated electronic records; structured communication; and staff training. Copyright © 2016 Elsevier Inc. All rights reserved.
Financing pharmaceuticals in transition economies.
Kanavos, P
1999-06-01
This paper (a) provides a methodological taxonomy of pricing, financing, reimbursement, and cost containment methodologies for pharmaceuticals; (b) analyzes complex agency relationships and the health versus industrial policy tradeoff; (c) pinpoints financing measures to balance safety and effectiveness of medicines and their affordability by publicly funded systems in transition; and (d) highlights viable options for policy-makers for the financing of pharmaceuticals in transition. Three categories of measures and their implications for pharmaceutical policy cost containing are analyzed: supply-side measures, targeting manufacturers, proxy demand-side measures, targeting physicians and pharmacists, and demand-side measures, targeting patients. In pursuing supply side measures, we explore free pricing for pharmaceuticals, direct price controls, cost-plus and cost pricing, average pricing and international price comparisons, profit control, reference pricing, the introduction of a fourth hurdle, positive and negative lists, and other price control measures. The analysis of proxy-demand measures includes budgets for physicians, generic policies, practice guidelines, monitoring the authorizing behavior of physicians, and disease management schemes. Demand-side measures explore the effectiveness of patient co-payments, the impact of allowing products over-the-counter and health promotion programs. Global policies should operate simultaneously on the supply, the proxy demand, and the demand-side. Policy-making needs to have a continuous long-term planning. The importation of policies into transition economy may require extensive and expensive adaptation, and/or lead to sub-optimal policy outcomes.
Transit pricing and performance
Pickerell, D.H.; Abkowitz, M.; Tozzi, J.; McCord, M.R.; Cheng, L.H.
1986-01-01
The 9 papers in the report deal with the following areas: Federal operating assistance for urban mass transit; a decade of experience; transit route characteristics and headway-based reliability control; day-of-week and part-of-month variation in bus ridership; job satisfaction and transit operator recognition programs; results of a survey of muni operators; bus marketing costs: the experience of 18 section 15 reporters from 1981 to 1983; prospects for differential transit pricing in the United States; an initial analysis of total factor productivity for public-transit coordination of transportation resources: the Georgia experience; absenteeism, accidents, and attrition: part-time versus full-time bus drivers.
Gifts from Exoplanetary Transits
NASA Astrophysics Data System (ADS)
Narita, Norio
2009-08-01
The discovery of transiting extrasolar planets has enabled us to do a number of interesting studies. Transit photometry reveals the radius and the orbital inclination of transiting planets, which allows us to learn the true mass and density of the respective planets by the combined information from radial velocity (RV) measurements. In addition, follow-up observations of transiting planets, looking at such things as secondary eclipses, transit timing variations, transmission spectroscopy, and the Rossiter-McLaughlin effect, provide us information about their dayside temperatures, unseen bodies in systems, planetary atmospheres, and the obliquity of planetary orbits. Such observational information, which will provide us a greater understanding of extrasolar planets, is available only for transiting planets. Here, I briefly summarize what we can learn from transiting planets and introduce previous studies.
NASA Technical Reports Server (NTRS)
Dubey, Pradeep K.; Flynn, Michael J.
1990-01-01
An effort is made to characterize the tradeoffs and overheads limiting the speedup potential theoretically projected for pipeline-incorporating computer architectures, using a mathematical model of the roles played by the various parameters. Pipeline optimization proceeds by a partitioning of the pipeline into an optimum number of segments so that maximization of throughput is obtained. Inferences are drawn from the model, and potential improvements to it are identified. Substantial agreement is obtained with Kunkel and Smith's (1986) CRAY-1S simulations of pipelining.
Enhanced optical transmission at the cutoff transition.
Laux, E; Genet, C; Ebbesen, T W
2009-04-27
The phenomenon of extraordinary transmission in the optical regime for circular hole arrays in optically thick metal films is studied as a function of hole size and depth. In the limit of small holes compared to the depth, the transmission properties follow a waveguide type behavior. By describing the transmission process as resulting from the interference between a resonant and a non-resonant contribution, a transition is clearly revealed through the specific spectral variations of the resonance at a given hole depth. This transition is associated to a change in the attenuation through the hole as its size increases, and corresponds to the optimal condition for surface plasmon excitation.
Transiting Exoplanet Survey Satellite (TESS)
NASA Astrophysics Data System (ADS)
Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland; Latham, David W.; Bakos, Gáspár Á.; Bean, Jacob L.; Berta-Thompson, Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David; Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty, John; De Lee, Nathan; Dressing, Courtney; Dunham, Edward W.; Endl, Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon M.; Jernigan, Garrett; Johnson, John Asher; Kaltenegger, Lisa; Kawai, Nobuyuki; Kjeldsen, Hans; Laughlin, Gregory; Levine, Alan M.; Lin, Douglas; Lissauer, Jack J.; MacQueen, Phillip; Marcy, Geoffrey; McCullough, Peter R.; Morton, Timothy D.; Narita, Norio; Paegert, Martin; Palle, Enric; Pepe, Francesco; Pepper, Joshua; Quirrenbach, Andreas; Rinehart, Stephen A.; Sasselov, Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti, Alessandro; Stassun, Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew; Torres, Guillermo; Udry, Stephane; Villasenor, Joel
2015-01-01
The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its 2-year mission, TESS will employ four wide-field optical charge-coupled device cameras to monitor at least 200,000 main-sequence dwarf stars with IC≈4-13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from 1 month to 1 year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10 to 100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every 4 months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.
Transiting Exoplanet Survey Satellite (TESS)
NASA Astrophysics Data System (ADS)
Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland; Latham, David W.; Bakos, Gáspár. Á.; Bean, Jacob L.; Berta-Thompson, Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David; Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty, John; De Lee, Nathan; Dressing, Courtney; Dunham, E. W.; Endl, Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon; Jernigan, Garrett; Johnson, John A.; Kaltenegger, Lisa; Kawai, Nobuyuki; Kjeldsen, Hans; Laughlin, Gregory; Levine, Alan M.; Lin, Douglas; Lissauer, Jack J.; MacQueen, Phillip; Marcy, Geoffrey; McCullough, P. R.; Morton, Timothy D.; Narita, Norio; Paegert, Martin; Palle, Enric; Pepe, Francesco; Pepper, Joshua; Quirrenbach, Andreas; Rinehart, S. A.; Sasselov, Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti, Alessandro; Stassun, Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew; Torres, Guillermo; Udry, Stephane; Villasenor, Joel
2014-08-01
The Transiting Exoplanet Survey Satellite (TESS ) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with IC (approximately less than) 13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.
Transition to turbulence in duct flow
NASA Astrophysics Data System (ADS)
Biau, Damien; Soueid, Houssam; Bottaro, Alessandro
The transition of the flow in a duct of square cross-section is studied. Like in the similar case of the pipe flow, the motion is linearly stable for all Reynolds numbers; this flow is thus a good candidate to investigate the path to turbulence. Initially the so-called is formulated and solved, yielding optimal disturbances in the form of longitudinal vortices. Such optimals, however, fail to elicit a significant response from the system in the nonlinear regime. Thus, streamwise-inhomogeneous sub-optimal disturbances are focused upon; nonlinear quadratic interactions are immediately caused by such initial perturbations and an unstable streamwise-homogeneous large-amplitude mode rapidly emerges. The subsequent evolution of the flow, at a value of the Reynolds number at the boundary between fully developed turbulence and relaminarization, shows the alternance of patterns with two pairs of large-scale vortices near opposing parallel walls. Such edge states bear a resemblance to optimal disturbances.
NASA Astrophysics Data System (ADS)
Vojta, Matthias
2003-12-01
In recent years, quantum phase transitions have attracted the interest of both theorists and experimentalists in condensed matter physics. These transitions, which are accessed at zero temperature by variation of a non-thermal control parameter, can influence the behaviour of electronic systems over a wide range of the phase diagram. Quantum phase transitions occur as a result of competing ground state phases. The cuprate superconductors which can be tuned from a Mott insulating to a d-wave superconducting phase by carrier doping are a paradigmatic example. This review introduces important concepts of phase transitions and discusses the interplay of quantum and classical fluctuations near criticality. The main part of the article is devoted to bulk quantum phase transitions in condensed matter systems. Several classes of transitions will be briefly reviewed, pointing out, e.g., conceptual differences between ordering transitions in metallic and insulating systems. An interesting separate class of transitions is boundary phase transitions where only degrees of freedom of a subsystem become critical; this will be illustrated in a few examples. The article is aimed at bridging the gap between high-level theoretical presentations and research papers specialized in certain classes of materials. It will give an overview on a variety of different quantum transitions, critically discuss open theoretical questions, and frequently make contact with recent experiments in condensed matter physics.
Characterizing the Superconducting-to-Normal Transition in Mo/Au Transition-Edge Sensor Bilayers
NASA Technical Reports Server (NTRS)
Smith, Stephen J.; Bandler, Simon R.; Brown, Ari. -D.; Chervenak, Jay A.; Finkbeiner, Fred M.; Iyomoto, Naoko; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.
2007-01-01
We are developing arrays of Mo/Au bilayer transition-edge sensors (TES's) for applications in future X-ray astronomy missions such as NASA's Constellation-X. The physical properties of the superconducting-to-normal transition in our TES bilayers, while often reproducible and characterized, are not well understood. The addition of normal metal features on top of the bilayer are found to change the shape and temperature of the transition, and they typically reduce the unexplained 'excess' noise. In order to understand and potentially optimize the properties of the transition, we have been studying the temperature, widths and current dependence of these transitions. We report on the characterization of devices both deposited on silicon substrates and suspended on thin silicon nitride membranes. This includes key device parameters such as the logarithmic resistance sensitivity with temperature alpha, and the logarithmic resistance sensitivity with current beta, of the phase-transition. We investigate alpha and beta as a function of current, both at fixed and varying bias points in the transition. Using Ginzburg-Landau theory for the current dependence of the superconducting transition temperature, we investigate the relationship between alpha and beta and compare our measured and theoretical estimates.
The periodontal prosthesis mode of transition to an implant-supported dentition.
Hunt, Peter; Norkin, Frederic; Serrano, Julian
2006-01-01
In recent years, implant-supported reconstructions have become a welcome alternative to dentures for those who have lost their natural dentition. While the benefits of the final implant-supported reconstruction may be obvious, the planning and execution of therapy to achieve this result may be bewildering to many dentists. Four main modes of transfer have evolved: an uncontrolled or "haphazard" transition; the traditional "dentures first" mode, an immediate transition, and a staged transition. This article proposes an additional mode of transition called periodontal prosthesis, which has the potential to make the transition process smoother and more predictable while providing optimal retention of alveolar supporting structures and generating optimal esthetics.
Coordinated and uncoordinated optimization of networks
NASA Astrophysics Data System (ADS)
Brede, Markus
2010-06-01
In this paper, we consider spatial networks that realize a balance between an infrastructure cost (the cost of wire needed to connect the network in space) and communication efficiency, measured by average shortest path length. A global optimization procedure yields network topologies in which this balance is optimized. These are compared with network topologies generated by a competitive process in which each node strives to optimize its own cost-communication balance. Three phases are observed in globally optimal configurations for different cost-communication trade offs: (i) regular small worlds, (ii) starlike networks, and (iii) trees with a center of interconnected hubs. In the latter regime, i.e., for very expensive wire, power laws in the link length distributions P(w)∝w-α are found, which can be explained by a hierarchical organization of the networks. In contrast, in the local optimization process the presence of sharp transitions between different network regimes depends on the dimension of the underlying space. Whereas for d=∞ sharp transitions between fully connected networks, regular small worlds, and highly cliquish periphery-core networks are found, for d=1 sharp transitions are absent and the power law behavior in the link length distribution persists over a much wider range of link cost parameters. The measured power law exponents are in agreement with the hypothesis that the locally optimized networks consist of multiple overlapping suboptimal hierarchical trees.
NASA Astrophysics Data System (ADS)
Hansteen, V.; Murdin, P.
2000-11-01
The SOLAR TRANSITION REGION comprises the PLASMA between the CHROMOSPHERE and the CORONA. In both of these regions the temperature is fairly uniform. The transition region, by contrast, is believed to be characterized by a very steep temperature rise from a chromospheric temperature of slightly less than 104 K to coronal temperatures on the order of 106 K. The goal of modeling the transition regi...
Transitional Care in Inflammatory Bowel Disease
2011-01-01
Transitional care is an organized effort to provide pediatric patients with the tools and resources they need to assume personal responsibility for their medical care while facilitating their transfer from a pediatrician to an adult practitioner. Since inflammatory bowel disease (IBD) is usually chronic and up to 25% of IBD patients are diagnosed before the age of 18 years, transitional care is an important consideration for adolescent and young adult patients. The importance of transitional care for chronic diseases that begin in childhood has been recognized in a number of published recommendations. However, most of these recommendations arise from intuitive reasoning, as physicians lack information regarding the need for transitional care, optimal delivery protocols, and the efficacy of transition programs. Even fewer studies have been published regarding transitional care in IBD. Current guidelines stress the importance of providing patients with educational resources to help them develop the skills they need to manage their care as independent adults, introducing the concept of transfer to adult care in advance of the actual transfer, and developing routes of communication to facilitate the transfer from pediatric to adult care providers. Future studies should aim to elucidate which programs are effective and how they should be implemented. PMID:21346849
Communication: Optimal parameters for basin-hopping global optimization based on Tsallis statistics
Shang, C. Wales, D. J.
2014-08-21
A fundamental problem associated with global optimization is the large free energy barrier for the corresponding solid-solid phase transitions for systems with multi-funnel energy landscapes. To address this issue we consider the Tsallis weight instead of the Boltzmann weight to define the acceptance ratio for basin-hopping global optimization. Benchmarks for atomic clusters show that using the optimal Tsallis weight can improve the efficiency by roughly a factor of two. We present a theory that connects the optimal parameters for the Tsallis weighting, and demonstrate that the predictions are verified for each of the test cases.
[SIAM conference on optimization
Not Available
1992-05-10
Abstracts are presented of 63 papers on the following topics: large-scale optimization, interior-point methods, algorithms for optimization, problems in control, network optimization methods, and parallel algorithms for optimization problems.
[SIAM conference on optimization
Not Available
1992-05-10
Abstracts are presented of 63 papers on the following topics: large-scale optimization, interior-point methods, algorithms for optimization, problems in control, network optimization methods, and parallel algorithms for optimization problems.
Energy management during the space shuttle transition.
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1972-01-01
An approach to calculating optimal, gliding flight paths of the type associated with the space shuttle's transition from entry to cruising flight is presented. Kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations, reducing the dimension and complexity of the problem. The capability for treating integral and terminal penalties (as well as Mach number effects) is retained in the numerical optimization; hence, stability and control boundaries can be observed as trajectories to the desired final energy, flight path angle, and range are determined. Numerical results show that the 'jump' to the 'front-side of the L/D curve' need not be made until the end of the transition and that the dynamic model provides a conservative range estimate. Alternatives for real-time trajectory control are discussed.
Energy management during the space shuttle transition
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1972-01-01
An approach to calculating optimal, gliding flight paths of the type associated with the space shuttle's transition from entry to cruising flight is presented. Kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations, reducing the dimension and complexity of the problem. The capability for treating integral and terminal penalties (as well as Mach number effects) is retained in the numerical optimization; hence, stability and control boundaries can be observed as trajectories to the desired final energy, flight path angle, and range are determined. Numerical results show that the jump to the front-side of the L/D curve need not be made until the end of the transition and that the dynamic model provides a conservative range estimate. Alternatives for real time trajectory control are discussed.
Transitioning unmanned ground vehicle research technologies
NASA Astrophysics Data System (ADS)
Pacis, E. Biagtan; Everett, H. R.; Farrington, N.; Kogut, G.; Sights, B.; Kramer, T.; Thompson, M.; Bruemmer, D.; Few, D.
2005-05-01
The Technology Transfer project employs a spiral development process to enhance the functionality and autonomy of mobile systems in the Joint Robotics Program (JRP) Robotic Systems Pool (RSP). The approach is to harvest prior and on-going developments that address the technology needs identified by emergent in-theatre requirements and users of the RSP. The component technologies are evaluated on a transition platform to identify the best features of the different approaches, which are then integrated and optimized to work in harmony in a complete solution. The result is an enabling mechanism that continuously capitalizes on state-of-the-art results from the research environment to create a standardized solution that can be easily transitioned to ongoing development programs. This paper focuses on particular research areas, specifically collision avoidance, simultaneous localization and mapping (SLAM), and target-following, and describes the results of their combined integration and optimization over the past 12 months.
Energy management during the space shuttle transition.
NASA Technical Reports Server (NTRS)
Stengel, R. F.
1972-01-01
An approach to calculating optimal, gliding flight paths of the type associated with the space shuttle's transition from entry to cruising flight is presented. Kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations, reducing the dimension and complexity of the problem. The capability for treating integral and terminal penalties (as well as Mach number effects) is retained in the numerical optimization; hence, stability and control boundaries can be observed as trajectories to the desired final energy, flight path angle, and range are determined. Numerical results show that the 'jump' to the 'front-side of the L/D curve' need not be made until the end of the transition and that the dynamic model provides a conservative range estimate. Alternatives for real-time trajectory control are discussed.
JTF CapMed Warrior Transition Division
2011-01-25
Injured Population To understand the complexity of Warrior Care 2 2011 MHS Conference Warrior Transition Division Mission Provide coordination and...integration of non- medical and medical services to ensure optimal Warrior care throughout the NCR JOA 3 2011 MHS Conference Understanding the Definition of...hostile-related injury or illness requiring long-term care that will require a Medical Evaluation Board (MEB) or Physical Evaluation Board (PEB) to
Transitive and Pseudo-Transitive Inferences
ERIC Educational Resources Information Center
Goodwin, Geoffrey P.; Johnson-Laird, P. N.
2008-01-01
Given that A is longer than B, and that B is longer than C, even 5-year-old children can infer that A is longer than C. Theories of reasoning based on formal rules of inference invoke simple axioms ("meaning postulates") to capture such transitive inferences. An alternative theory proposes instead that reasoners construct mental models of the…
Transition to Old Age (Transition to Retirement).
ERIC Educational Resources Information Center
Bergman, Simon
Several conceptualizations and definitions of retirement have been proposed. One of them--the three-stage transition process--can be illustrated from studies in Israel: (1) leaving the old role; (2) going through the act of formal separation; and (3) adjusting to the new situation and role. Today's higher rate of survival into later years means…
[From epidemiological transition to health transition].
Meslé, F; Vallin, J
2007-12-01
The "Epidemiological Transition" concept proposed by Abdel Omran in 1971 was the first theory attempting to explain the extraordinary progess that industrialized countries have achieved in health since the 18th century. Within the broader framework of the demographic transition, an important implication of this concept was that life expectancy in modern societies would converge toward limits determined by the new epidemiological conditions. In the ensuing decades, however the convergence process appears to have stopped as a result of a number of setbacks including the health crisis in Eastern Europe and AIDS in Africa. These setbacks do not fundamentally contradict the theory. A much greater contradiction was the unexpected dramatic decrease in cardiovascular disease that began as early as the 70s and had a major positive impact on life expectancy. Based on the concept of "Health Transition" described by Julio Frenk et al., we propose a complete revision of the health implications of the demographic transition based the idea of successive cycles of divergences/convergences induced by the appearance and generalization of major breakthroughs in health technologies and strategies. Three such cycles can be clearly identified on an international level corresponding to control of infectious then cardiovascular diseases, and perhaps most recently to the initial successes achieved in the field of ageing.
Brain Performance versus Phase Transitions
NASA Astrophysics Data System (ADS)
Torres, Joaquín J.; Marro, J.
2015-07-01
We here illustrate how a well-founded study of the brain may originate in assuming analogies with phase-transition phenomena. Analyzing to what extent a weak signal endures in noisy environments, we identify the underlying mechanisms, and it results a description of how the excitability associated to (non-equilibrium) phase changes and criticality optimizes the processing of the signal. Our setting is a network of integrate-and-fire nodes in which connections are heterogeneous with rapid time-varying intensities mimicking fatigue and potentiation. Emergence then becomes quite robust against wiring topology modification—in fact, we considered from a fully connected network to the Homo sapiens connectome—showing the essential role of synaptic flickering on computations. We also suggest how to experimentally disclose significant changes during actual brain operation.
ERIC Educational Resources Information Center
McNair, Jeff, Ed.; Kronick, Nancy, Ed.
Six papers address issues in the transition of students with disabilities into the adult world of work. In "Workplace Support," Jeff McNair defines "support," differentiates types of support, and considers various foci of intervention. The second paper titled, "Cross-Cultural Transition: An Exigent Topic for Study" by Nancy Kronick, reviews…
School Transition Bibliography.
ERIC Educational Resources Information Center
Pautler, Albert
This bibliography on school transition includes 240 entries of books, journal articles, papers, reports, bibliographies, and dissertations. These entries deal with transitions of the following populations: adult learners, youth, Plains Indian women, high school students, people with learning disabilities, disadvantaged youth, high school…
Transition Coordinators: Define Yourselves.
ERIC Educational Resources Information Center
Asselin, Susan B.; Todd-Allen, Mary; deFur, Sharon
1998-01-01
Describes a technique that was used successfully to identify the changing roles and responsibilities of special educators as transition coordinators. The Developing a Curriculum (DACUM) model uses people who are currently working in the occupation to define job responsibilities. The duties of a transition coordinator are identified. (CR)
Good Transitions = Great Starts!
ERIC Educational Resources Information Center
Our Children: The National PTA Magazine, 2012
2012-01-01
The smooth transition of outgoing and incoming board members and officers is of vital importance and can determine the PTA's success for years to come. The transition process is the responsibility of both incoming and outgoing officers and board members. It gives closure to those leaving their positions and allows those coming in to be properly…
ERIC Educational Resources Information Center
Regenwetter, Michel; Dana, Jason; Davis-Stober, Clintin P.
2011-01-01
Transitivity of preferences is a fundamental principle shared by most major contemporary rational, prescriptive, and descriptive models of decision making. To have transitive preferences, a person, group, or society that prefers choice option "x" to "y" and "y" to "z" must prefer "x" to…
Anderson, Lara B.; Gray, James; Raghuram, Nikhil; Taylor, Washington
2016-04-13
In this study, we explore a novel type of transition in certain 6D and 4D quantum field theories, in which the matter content of the theory changes while the gauge group and other parts of the spectrum remain invariant. Such transitions can occur, for example, for SU(6) and SU(7) gauge groups, where matter fields in a three-index antisymmetric representation and the fundamental representation are exchanged in the transition for matter in the two-index antisymmetric representation. These matter transitions are realized by passing through superconformal theories at the transition point. We explore these transitions in dual F-theory and heterotic descriptions, where a number of novel features arise. For example, in the heterotic description the relevant 6D SU(7) theories are described by bundles on K3 surfaces where the geometry of the K3 is constrained in addition to the bundle structure. On the F-theory side, non-standard representations such as the three-index antisymmetric representation of SU(N) require Weierstrass models that cannot be realized from the standard SU(N) Tate form. We also briefly describe some other situations, with groups such as Sp(3), SO(12), and SU(3), where analogous matter transitions can occur between different representations. For SU(3), in particular, we find a matter transition between adjoint matter and matter in the symmetric representation, giving an explicit Weierstrass model for the F-theory description of the symmetric representation that complements another recent analogous construction.
ERIC Educational Resources Information Center
Test, David W.
2008-01-01
Postschool outcomes for students with disabilities have been dismal for quite some time now. Although recent data from the National Longitudinal Transition Study 2 indicate some improvement, students with severe intellectual disabilities continue to transition into segregated employment at unacceptable rates in spite of a multitude of studies,…
Expanding Views on Transition.
ERIC Educational Resources Information Center
Repetto, Jeanne B.; Correa, Vivian I.
1996-01-01
This position paper proposes an expanded definition of transition, based on common components of early childhood and secondary perspectives. It advocates for a seamless model of transition service delivery for students with disabilities, including program planning, from birth through age 21. The model addresses curriculum, location of services,…
ERIC Educational Resources Information Center
Repetto, Jeanne B.
2003-01-01
Discussion of transition for students with disabilities emphasizes transition skills needed for life beyond work. The importance of assisting students in planning for their life roles as workers, family members, friends, consumers, and community members is discussed. Suggestions are offered to better prepare students for all their life roles by…
Transitioning between Clerkship Directors
ERIC Educational Resources Information Center
Soltys, Stephen M.; Pary, Robert J.; Robinson, Stephen W.; Markwell, Stephen J.
2011-01-01
Objective: The authors report on succession-planning for mid-level academic positions. Method: The authors describe the process of succession-planning between clerkship directors and the smooth transition resulting in one case. Results: Gradually transitioning allowed a new faculty person to assume the clerkship-director position with minimal…
Modeling the transition region
NASA Astrophysics Data System (ADS)
Singer, Bart A.
1994-04-01
The calculation of engineering flows undergoing laminar-turbulent transition presents special problems. Mean-flow quantities obey neither the fully laminar nor the fully turbulent correlations. In addition, local maxima in skin friction, wall temperature, and heat transfer often occur near the end of the transition region. Traditionally, modeling this region has been important for the design of turbine blades, where the transition region is long in relation to the chord length of the blade. More recently, the need for better transition-region models has been recognized by designers of hypersonic vehicles where the high Mach number, the low Reynolds number, and the low-disturbance flight environment emphasize the importance of the transition region. Needless to say, a model that might work well for the transitional flows typically found in gas turbines will not necessarily work well for the external surface of a hypersonic vehicle. In Section 2 of this report, some of the important flow features that control the transition region will be discussed. In Section 3, different approaches to the modeling problem will be summarized and cataloged. Fully turbulent flow models will be discussed in detail in Section 4; models specifically designed for transitional flow, in Section 5; and the evaluation of models, in Section 6.
Outplacement as Transition Counseling.
ERIC Educational Resources Information Center
Mirabile, Richard J.
1984-01-01
The author discusses five predictable stages of development in transition counseling. They include comfort (reassurances about self-worth and identity); reflection (exploration and understanding); clarification (with respect to career and self); direction (exploring possible life/career directions); and perspective shift (putting the transition in…
Transitions in Spousal Caregiving.
ERIC Educational Resources Information Center
Burton, Lynda C.; Zdaniuk, Bozena; Schulz, Richard; Jackson, Sharon; Hirsch, Calvin
2003-01-01
Describes transitions over 5 years among community-dwelling elderly spouses into and within caregiving roles and associated health outcomes. The trajectory of health outcomes associated with caregiving was generally downward. Those who transitioned to heavy caregiving had more symptoms of depression, and poorer self-reported health and health…
ERIC Educational Resources Information Center
Regenwetter, Michel; Dana, Jason; Davis-Stober, Clintin P.
2011-01-01
Transitivity of preferences is a fundamental principle shared by most major contemporary rational, prescriptive, and descriptive models of decision making. To have transitive preferences, a person, group, or society that prefers choice option "x" to "y" and "y" to "z" must prefer "x" to…
Transitioning between Clerkship Directors
ERIC Educational Resources Information Center
Soltys, Stephen M.; Pary, Robert J.; Robinson, Stephen W.; Markwell, Stephen J.
2011-01-01
Objective: The authors report on succession-planning for mid-level academic positions. Method: The authors describe the process of succession-planning between clerkship directors and the smooth transition resulting in one case. Results: Gradually transitioning allowed a new faculty person to assume the clerkship-director position with minimal…
2016-05-09
The planet Mercury is seen in silhouette, lower center of image, as it transits across the face of the sun, Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
The planet Mercury is seen in silhouette, lower third of image, as it transits across the face of the sun Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
The planet Mercury is seen in silhouette, lower left of image, as it transits across the face of the sun, Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
The planet Mercury is seen in silhouette, lower left, as it transits across the face of the sun Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
Nonlinear Transient Growth and Boundary Layer Transition
NASA Technical Reports Server (NTRS)
Paredes, Pedro; Choudhari, Meelan M.; Li, Fei
2016-01-01
Parabolized stability equations (PSE) are used in a variational approach to study the optimal, non-modal disturbance growth in a Mach 3 at plate boundary layer and a Mach 6 circular cone boundary layer. As noted in previous works, the optimal initial disturbances correspond to steady counter-rotating streamwise vortices, which subsequently lead to the formation of streamwise-elongated structures, i.e., streaks, via a lift-up effect. The nonlinear evolution of the linearly optimal stationary perturbations is computed using the nonlinear plane-marching PSE for stationary perturbations. A fully implicit marching technique is used to facilitate the computation of nonlinear streaks with large amplitudes. To assess the effect of the finite-amplitude streaks on transition, the linear form of plane- marching PSE is used to investigate the instability of the boundary layer flow modified by spanwise periodic streaks. The onset of bypass transition is estimated by using an N- factor criterion based on the amplification of the streak instabilities. Results show that, for both flow configurations of interest, streaks of sufficiently large amplitude can lead to significantly earlier onset of transition than that in an unperturbed boundary layer without any streaks.
Allahverdyan, Armen E; Hovhannisyan, Karen; Mahler, Guenter
2010-05-01
We study a refrigerator model which consists of two n -level systems interacting via a pulsed external field. Each system couples to its own thermal bath at temperatures T h and T c, respectively (θ ≡ T c/T h < 1). The refrigerator functions in two steps: thermally isolated interaction between the systems driven by the external field and isothermal relaxation back to equilibrium. There is a complementarity between the power of heat transfer from the cold bath and the efficiency: the latter nullifies when the former is maximized and vice versa. A reasonable compromise is achieved by optimizing the product of the heat-power and efficiency over the Hamiltonian of the two systems. The efficiency is then found to be bounded from below by [formula: see text] (an analog of the Curzon-Ahlborn efficiency), besides being bound from above by the Carnot efficiency [formula: see text]. The lower bound is reached in the equilibrium limit θ → 1. The Carnot bound is reached (for a finite power and a finite amount of heat transferred per cycle) for ln n > 1. If the above maximization is constrained by assuming homogeneous energy spectra for both systems, the efficiency is bounded from above by ζ CA and converges to it for n > 1.
NASA Astrophysics Data System (ADS)
Allahverdyan, Armen E.; Hovhannisyan, Karen; Mahler, Guenter
2010-05-01
We study a refrigerator model which consists of two n -level systems interacting via a pulsed external field. Each system couples to its own thermal bath at temperatures Th and Tc , respectively (θ≡Tc/Th<1) . The refrigerator functions in two steps: thermally isolated interaction between the systems driven by the external field and isothermal relaxation back to equilibrium. There is a complementarity between the power of heat transfer from the cold bath and the efficiency: the latter nullifies when the former is maximized and vice versa. A reasonable compromise is achieved by optimizing the product of the heat-power and efficiency over the Hamiltonian of the two systems. The efficiency is then found to be bounded from below by ζCA=(1)/(1-θ)-1 (an analog of the Curzon-Ahlborn efficiency), besides being bound from above by the Carnot efficiency ζC=(1)/(1-θ)-1 . The lower bound is reached in the equilibrium limit θ→1 . The Carnot bound is reached (for a finite power and a finite amount of heat transferred per cycle) for lnn≫1 . If the above maximization is constrained by assuming homogeneous energy spectra for both systems, the efficiency is bounded from above by ζCA and converges to it for n≫1 .
Modeling and Fitting Exoplanet Transit Light Curves
NASA Astrophysics Data System (ADS)
Millholland, Sarah; Ruch, G. T.
2013-01-01
We present a numerical model along with an original fitting routine for the analysis of transiting extra-solar planet light curves. Our light curve model is unique in several ways from other available transit models, such as the analytic eclipse formulae of Mandel & Agol (2002) and Giménez (2006), the modified Eclipsing Binary Orbit Program (EBOP) model implemented in Southworth’s JKTEBOP code (Popper & Etzel 1981; Southworth et al. 2004), or the transit model developed as a part of the EXOFAST fitting suite (Eastman et al. in prep.). Our model employs Keplerian orbital dynamics about the system’s center of mass to properly account for stellar wobble and orbital eccentricity, uses a unique analytic solution derived from Kepler’s Second Law to calculate the projected distance between the centers of the star and planet, and calculates the effect of limb darkening using a simple technique that is different from the commonly used eclipse formulae. We have also devised a unique Monte Carlo style optimization routine for fitting the light curve model to observed transits. We demonstrate that, while the effect of stellar wobble on transit light curves is generally small, it becomes significant as the planet to stellar mass ratio increases and the semi-major axes of the orbits decrease. We also illustrate the appreciable effects of orbital ellipticity on the light curve and the necessity of accounting for its impacts for accurate modeling. We show that our simple limb darkening calculations are as accurate as the analytic equations of Mandel & Agol (2002). Although our Monte Carlo fitting algorithm is not as mathematically rigorous as the Markov Chain Monte Carlo based algorithms most often used to determine exoplanetary system parameters, we show that it is straightforward and returns reliable results. Finally, we show that analyses performed with our model and optimization routine compare favorably with exoplanet characterizations published by groups such as the
Time-optimal control of rolling bodies
NASA Astrophysics Data System (ADS)
Perantoni, Giacomo; Limebeer, David J. N.
2013-11-01
The brachistochrone problem is usually solved in classical mechanics courses using the calculus of variations, although it is quintessentially an optimal control problem. In this paper, we address the classical brachistochrone problem and two vehicle-relevant generalisations from an optimal control perspective. We use optimal control arguments to derive closed-form solutions for both the optimal trajectory and the minimum achievable transit time for these generalisations. We then study optimal control problems involving a steerable disc rolling between prescribed points on the interior surface of a hemisphere. The effects of boundary and control constraints are examined. For three-dimensional problems of this type, which involve rolling bodies and nonholonomic constraints, numerical solutions are used.
Transition Implementation Guide. Instructor Materials.
ERIC Educational Resources Information Center
Boyer-Stephens, Arden, Ed.
This transition model, called Guiding Education toward Adult Roles for Success (GEARS), provides a comprehensive framework from which transition services and programs can evolve. Three components of transition services are considered: transition partners, the transition process, and adult outcomes. After an introduction, the report's second…
Phase Transitions in Living Neural Networks
NASA Astrophysics Data System (ADS)
Williams-Garcia, Rashid Vladimir
Our nervous systems are composed of intricate webs of interconnected neurons interacting in complex ways. These complex interactions result in a wide range of collective behaviors with implications for features of brain function, e.g., information processing. Under certain conditions, such interactions can drive neural network dynamics towards critical phase transitions, where power-law scaling is conjectured to allow optimal behavior. Recent experimental evidence is consistent with this idea and it seems plausible that healthy neural networks would tend towards optimality. This hypothesis, however, is based on two problematic assumptions, which I describe and for which I present alternatives in this thesis. First, critical transitions may vanish due to the influence of an environment, e.g., a sensory stimulus, and so living neural networks may be incapable of achieving "critical" optimality. I develop a framework known as quasicriticality, in which a relative optimality can be achieved depending on the strength of the environmental influence. Second, the power-law scaling supporting this hypothesis is based on statistical analysis of cascades of activity known as neuronal avalanches, which conflate causal and non-causal activity, thus confounding important dynamical information. In this thesis, I present a new method to unveil causal links, known as causal webs, between neuronal activations, thus allowing for experimental tests of the quasicriticality hypothesis and other practical applications.
Predictability of critical transitions
NASA Astrophysics Data System (ADS)
Zhang, Xiaozhu; Kuehn, Christian; Hallerberg, Sarah
2015-11-01
Critical transitions in multistable systems have been discussed as models for a variety of phenomena ranging from the extinctions of species to socioeconomic changes and climate transitions between ice ages and warm ages. From bifurcation theory we can expect certain critical transitions to be preceded by a decreased recovery from external perturbations. The consequences of this critical slowing down have been observed as an increase in variance and autocorrelation prior to the transition. However, especially in the presence of noise, it is not clear whether these changes in observation variables are statistically relevant such that they could be used as indicators for critical transitions. In this contribution we investigate the predictability of critical transitions in conceptual models. We study the quadratic integrate-and-fire model and the van der Pol model under the influence of external noise. We focus especially on the statistical analysis of the success of predictions and the overall predictability of the system. The performance of different indicator variables turns out to be dependent on the specific model under study and the conditions of accessing it. Furthermore, we study the influence of the magnitude of transitions on the predictive performance.
NASA Astrophysics Data System (ADS)
Cameron, Andrew Collier
An extrasolar planet will transit the visible hemisphere of its host star if its orbital plane lies sufficiently close to the observer's line of sight. The resulting periodic dips in stellar flux reveal key system parameters, including the density of the host star and, if radial-velocity observations are available, the surface gravitational acceleration of the planet. In this chapter I present the essential methodology for modelling the time-dependent flux variation during a transit, and its use in determining the posterior probability distribution for the physical parameters of the system. Large-scale searches for transiting systems are an efficient way of discovering planets whose bulk densities, and hence compositions, can be accessed if their masses can also be determined. I present algorithms for detrending large ensembles of light curves, for searching for transit-like signals among them. I also discuss methods for identifying diluted stellar eclipsing binaries mimicking planetary transit signals, and validation of transit candidates too faint for radial-velocity follow-up. I review the use of time-resolved spectrophotometry and high-resolution spectroscopy during transits to identify the molecular constituents of exoplanetary atmospheres.
Milestoning with transition memory
NASA Astrophysics Data System (ADS)
Hawk, Alexander T.; Makarov, Dmitrii E.
2011-12-01
Milestoning is a method used to calculate the kinetics and thermodynamics of molecular processes occurring on time scales that are not accessible to brute force molecular dynamics (MD). In milestoning, the conformation space of the system is sectioned by hypersurfaces (milestones), an ensemble of trajectories is initialized on each milestone, and MD simulations are performed to calculate transitions between milestones. The transition probabilities and transition time distributions are then used to model the dynamics of the system with a Markov renewal process, wherein a long trajectory of the system is approximated as a succession of independent transitions between milestones. This approximation is justified if the transition probabilities and transition times are statistically independent. In practice, this amounts to a requirement that milestones are spaced such that trajectories lose position and velocity memory between subsequent transitions. Unfortunately, limiting the number of milestones limits both the resolution at which a system's properties can be analyzed, and the computational speedup achieved by the method. We propose a generalized milestoning procedure, milestoning with transition memory (MTM), which accounts for memory of previous transitions made by the system. When a reaction coordinate is used to define the milestones, the MTM procedure can be carried out at no significant additional expense as compared to conventional milestoning. To test MTM, we have applied its version that allows for the memory of the previous step to the toy model of a polymer chain undergoing Langevin dynamics in solution. We have computed the mean first passage time for the chain to attain a cyclic conformation and found that the number of milestones that can be used, without incurring significant errors in the first passage time is at least 8 times that permitted by conventional milestoning. We further demonstrate that, unlike conventional milestoning, MTM permits
Transition nozzle combustion system
Kim, Won-Wook; McMahan, Kevin Weston; Maldonado, Jaime Javier
2016-11-29
The present application provides a combustion system for use with a cooling flow. The combustion system may include a head end, an aft end, a transition nozzle extending from the head end to the aft end, and an impingement sleeve surrounding the transition nozzle. The impingement sleeve may define a first cavity in communication with the head end for a first portion of the cooling flow and a second cavity in communication with the aft end for a second portion of the cooling flow. The transition nozzle may include a number of cooling holes thereon in communication with the second portion of the cooling flow.
Holographic magnetic phase transition
Lifschytz, Gilad; Lippert, Matthew
2009-09-15
We study four-dimensional interacting fermions in a strong magnetic field, using the holographic Sakai-Sugimoto model of intersecting D4- and D8-branes in the deconfined, chiral-symmetric parallel phase. We find that as the magnetic field is varied, while staying in the parallel phase, the fermions exhibit a first-order phase transition in which their magnetization jumps discontinuously. Properties of this transition are consistent with a picture in which some of the fermions jump to the lowest Landau level. Similarities to known magnetic phase transitions are discussed.
Gollub, Caroline; Kowalewski, Markus; de Vivie-Riedle, Regina
2008-08-15
We present a modified optimal control scheme based on the Krotov method, which allows for strict limitations on the spectrum of the optimized laser fields. A frequency constraint is introduced and derived mathematically correct, without losing monotonic convergence of the algorithm. The method guarantees a close link to learning loop control experiments and is demonstrated for the challenging control of nonresonant Raman transitions, which are used to implement a set of global quantum gates for molecular vibrational qubits.
On the Parameterized Complexity of Some Optimization Problems Related to Multiple-Interval Graphs
NASA Astrophysics Data System (ADS)
Jiang, Minghui
We show that for any constant t ≥ 2, K -Independent Set and K-Dominating Set in t-track interval graphs are W[1]-hard. This settles an open question recently raised by Fellows, Hermelin, Rosamond, and Vialette. We also give an FPT algorithm for K-Clique in t-interval graphs, parameterized by both k and t, with running time max { t O(k), 2 O(klogk) } ·poly(n), where n is the number of vertices in the graph. This slightly improves the previous FPT algorithm by Fellows, Hermelin, Rosamond, and Vialette. Finally, we use the W[1]-hardness of K-Independent Set in t-track interval graphs to obtain the first parameterized intractability result for a recent bioinformatics problem called Maximal Strip Recovery (MSR). We show that MSR-d is W[1]-hard for any constant d ≥ 4 when the parameter is either the total length of the strips, or the total number of adjacencies in the strips, or the number of strips in the optimal solution.
Momentum injection in tokamak plasmas and transitions to reduced transport.
Parra, F I; Barnes, M; Highcock, E G; Schekochihin, A A; Cowley, S C
2011-03-18
The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.
Natural laminar-turbulent transition delay by dielectric barrier discharge
NASA Astrophysics Data System (ADS)
Ustinov, Maxim; Kogan, Mikhail; Litvinov, Vladimir; Uspensky, Alexander
2011-12-01
The use dielectric barrier discharge for the delay of laminar turbulent transition excited by natural flow disturbances in a quiet wind-tunnel was investigated experimentally. Optimal electrodes location and the operational regime of high-voltage impulse generator provided maximal downstream shift of transition location were found. It was demonstrated that the 10% increase of the laminar part of boundary layer can be obtained using barrier discharge with the cross-flow electrodes. This gives up to 20% friction drag reduction.
Momentum Injection in Tokamak Plasmas and Transitions to Reduced Transport
Parra, F. I.; Highcock, E. G.; Schekochihin, A. A.; Barnes, M.
2011-03-18
The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.
Frequency domain quantum optimal control under multiple constraints
NASA Astrophysics Data System (ADS)
Shu, Chuan-Cun; Ho, Tak-San; Xing, Xi; Rabitz, Herschel
2016-03-01
Optimal control of quantum systems with complex constrained external fields is one of the longstanding theoretical and numerical challenges at the frontier of quantum control research. Here, we present a theoretical method that can be utilized to optimize the control fields subject to multiple constraints while guaranteeing monotonic convergence towards desired physical objectives. This optimization method is formulated in the frequency domain in line with the current ultrafast pulse shaping technique, providing the possibility for performing quantum optimal control simulations and experiments in a unified fashion. For illustrations, this method is successfully employed to perform multiple constraint spectral-phase-only optimization for maximizing resonant multiphoton transitions with desired pulses.
Multiple Satellite Trajectory Optimization
2004-12-01
SOLVING OPTIMAL CONTROL PROBLEMS ........................................5...OPTIMIZATION A. SOLVING OPTIMAL CONTROL PROBLEMS The driving principle used to solve optimal control problems was first formalized by the Soviet...methods and processes of solving optimal control problems , this section will demonstrate how the formulations work as expected. Once coded, the
The animation shows the difference between planet transit timing of single and multiple planet system. In tightly packed planetary systems, the gravitational pull of the planets among themselves ca...
Oligocyclopentadienyl transition metal complexes
de Azevedo, Cristina G.; Vollhardt, K. Peter C.
2002-01-18
Synthesis, characterization, and reactivity studies of oligocyclopentadienyl transition metal complexes, namely those of fulvalene, tercyclopentadienyl, quatercyclopentadienyl, and pentacyclopentadienyl(cyclopentadienyl) are the subject of this account. Thermal-, photo-, and redox chemistries of homo- and heteropolynuclear complexes are described.
ERIC Educational Resources Information Center
Bendersky, Nora; And Others
1984-01-01
Describes a workshop for nine South American students at the Hebrew University of Jerusalem. The two-day session focussed on exploring coping behaviors that could help students adjust to transitions. (JAC)
ERIC Educational Resources Information Center
Bendersky, Nora; And Others
1984-01-01
Describes a workshop for nine South American students at the Hebrew University of Jerusalem. The two-day session focussed on exploring coping behaviors that could help students adjust to transitions. (JAC)
Superconductivity in transition metals.
Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P
2015-03-13
A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Alternative fuel transit buses
Motta, R.; Norton, P.; Kelly, K.
1996-10-01
The National Renewable Energy Laboratory (NREL) is a U.S. Department of Energy (DOE) national laboratory; this project was funded by DOE. One of NREL`s missions is to objectively evaluate the performance, emissions, and operating costs of alternative fuel vehicles so fleet managers can make informed decisions when purchasing them. Alternative fuels have made greater inroads into the transit bus market than into any other. Each year, the American Public Transit Association (APTA) surveys its members on their inventory and buying plans. The latest APTA data show that about 4% of the 50,000 transit buses in its survey run on an alternative fuel. Furthermore, 1 in 5 of the new transit buses that members have on order are alternative fuel buses. This program was designed to comprehensively and objectively evaluate the alternative fuels in use in the industry.
Palaeontology: turtles in transition.
Lee, Michael S Y
2013-06-17
One of the major remaining gaps in the vertebrate fossil record concerns the origin of turtles. The enigmatic little reptile Eunotosaurus could represent an important transitional form, as it has a rudimentary shell that resembles the turtle carapace.
Use of Decoys to Optimize an All-Atom Force Field Including Hydration
Arnautova, Yelena A.; Scheraga, Harold A.
2008-01-01
A novel method of parameter optimization is proposed. It makes use of large sets of decoys generated for six nonhomologous proteins with different architecture. Parameter optimization is achieved by creating a free energy gap between sets of nativelike and nonnative conformations. The method is applied to optimize the parameters of a physics-based scoring function consisting of the all-atom ECEPP05 force field coupled with an implicit solvent model (a solvent-accessible surface area model). The optimized force field is able to discriminate near-native from nonnative conformations of the six training proteins when used either for local energy minimization or for short Monte Carlo simulated annealing runs after local energy minimization. The resulting force field is validated with an independent set of six nonhomologous proteins, and appears to be transferable to proteins not included in the optimization; i.e., for five out of the six test proteins, decoys with 1.7- to 4.0-Å all-heavy-atom root mean-square deviations emerge as those with the lowest energy. In addition, we examined the set of misfolded structures created by Park and Levitt using a four-state reduced model. The results from these additional calculations confirm the good discriminative ability of the optimized force field obtained with our decoy sets. PMID:18502794
Urban guideway transit workshop: Proceedings
Larsen, H. )
1992-03-01
On March 20--21, 1991, EPRI sponsored a workshop on urban guideway transit. The purpose of this workshop was to provide utility managers with increased knowledge about urban guideway transit options, public policy regarding transit, and the effect of transit options on utility operations. With this information utilities should be better prepared to make decisions about transit development in their service areas. The workshop also provided EPRI with ideas and information for developing an R D project plan for urban guideway transit.
2011-05-01
Park, NC 27709-2211 15. SUBJECT TERMS Quantum Thoery Phase transitions Subir Sachdev Harvard University Office of Sponsored Research 1350...magnetism, and solvable models obtained from string theory. After introducing the basic theory, it moves on to a detailed description of the canonical...students and researchers in condensed matter physics and particle and string theory. Print | Close Quantum Phase Transitions 2nd Edition Subir Sachdev
Anderson, Lara B.; Gray, James; Raghuram, Nikhil; ...
2016-04-13
In this study, we explore a novel type of transition in certain 6D and 4D quantum field theories, in which the matter content of the theory changes while the gauge group and other parts of the spectrum remain invariant. Such transitions can occur, for example, for SU(6) and SU(7) gauge groups, where matter fields in a three-index antisymmetric representation and the fundamental representation are exchanged in the transition for matter in the two-index antisymmetric representation. These matter transitions are realized by passing through superconformal theories at the transition point. We explore these transitions in dual F-theory and heterotic descriptions, wheremore » a number of novel features arise. For example, in the heterotic description the relevant 6D SU(7) theories are described by bundles on K3 surfaces where the geometry of the K3 is constrained in addition to the bundle structure. On the F-theory side, non-standard representations such as the three-index antisymmetric representation of SU(N) require Weierstrass models that cannot be realized from the standard SU(N) Tate form. We also briefly describe some other situations, with groups such as Sp(3), SO(12), and SU(3), where analogous matter transitions can occur between different representations. For SU(3), in particular, we find a matter transition between adjoint matter and matter in the symmetric representation, giving an explicit Weierstrass model for the F-theory description of the symmetric representation that complements another recent analogous construction.« less
2016-05-09
Boyertown Area High School astronomy teacher Peter Detterline prepares high powered binoculars with a solar filter so that his students may view the planet Mercury as it transits across the face of the sun , Monday, May 9, 2016, Boyertown Area High School, Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
Boyertown Area High School students, 12th grader Bransen Mackey, left, and 11th grader Nick Cioppi wear solar safety glasses and attempt to see the planet Mercury as it transits across the face of the sun, Monday, May 9, 2016, Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
Boyertown Area High School 12th grade student Ben Maurer uses his smartphone and a photographers lens with a solar filter to make a photograph of the planet Mercury transitting the sun, Monday, May 9, 2016, Boyertown area High School, Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
2016-05-09
Boyertown Area High School 12th grade student Jay Hallman looks through a photographers lens and solar filter to see the planet Mercury as it transits across the face of the sun , Monday, May 9, 2016, Boyertown area High School, Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Photo Credit: (NASA/Bill Ingalls)
Critical transition in the constrained traveling salesman problem
NASA Astrophysics Data System (ADS)
Andrecut, M.; Ali, M. K.
2001-04-01
We investigate the finite size scaling of the mean optimal tour length as a function of density of obstacles in a constrained variant of the traveling salesman problem (TSP). The computational experience pointed out a critical transition (at ρc~85%) in the dependence between the excess of the mean optimal tour length over the Held-Karp lower bound and the density of obstacles.
Sharp transitions in low-number quantum dots Bayesian magnetometry
NASA Astrophysics Data System (ADS)
Mazurek, Paweł; Horodecki, Michał; Czekaj, Łukasz; Horodecki, Paweł
2016-09-01
We consider Bayesian estimate of static magnetic field, characterized by a prior Gaussian probability distribution, in systems of a few electron quantum dot spins interacting with infinite temperature spin environment via hyperfine interaction. Sudden transitions among optimal states and measurements are observed. Usefulness of measuring occupation levels is shown for all times of the evolution, together with the role of entanglement in the optimal scenario. For low values of magnetic field, memory effects stemming from the interaction with environment provide limited metrological advantage.
A Flexible Transition State Searching Method for Atmospheric Reaction Systems
Lin, Xiao-Xiao; Liu, Yi-Rong; Huang, Teng; Chen, Jiao; Jiang, Shuai; Huang, Wei
2015-04-01
The precise and rapid exploration of transition states (TSs) is a major challenge when studying atmospheric reactions due to their complexity. In this work, a Monte Carlo Transition State Search Method (MCTSSM), which integrates Monte Carlo sampling technique with transition state optimization methods using an efficient computer script, has been developed for transition state searches. The efficiency and the potential application in atmospheric reactions of this method have been demonstrated by three types of test suits related to the reactions of atmospheric volatile organic compounds (VOCs): (1) OH addition, (2) OH hydrogen-abstraction, and (3) the other reactive group (e.g. Cl, O3, NO3), especially for the reaction of β-pinene-sCI (stabilized Criegee Intermediates) with water. It was shown that the application of this method with effective restricted parameters has greatly simplified the time-consuming and tedious manual search procedure for transition state (TS) of the bimolecular reaction systems.
A flexible transition state searching method for atmospheric reaction systems
NASA Astrophysics Data System (ADS)
Lin, Xiao-Xiao; Liu, Yi-Rong; Huang, Teng; Chen, Jiao; Jiang, Shuai; Huang, Wei
2015-04-01
The precise and rapid exploration of transition states (TSs) is a major challenge when studying atmospheric reactions due to their complexity. In this work, a Monte Carlo Transition State Search Method (MCTSSM), which integrates Monte Carlo sampling technique with transition state optimization methods using an efficient computer script, has been developed for transition state searches. The efficiency and the potential application in atmospheric reactions of this method have been demonstrated by three types of test suits related to the reactions of atmospheric volatile organic compounds (VOCs): (1) OH addition, (2) OH hydrogen-abstraction, and (3) the other reactive group (e.g. Cl, O3, NO3), especially for the reaction of β-pinene-sCI (stabilized Criegee Intermediates) with water. It was shown that the application of this method with effective restricted parameters has greatly simplified the time-consuming and tedious manual search procedure for transition state (TS) of the bimolecular reaction systems.
Effect of Transition Aerodynamics on Aeroassist Flight Experiment Trajectories
NASA Technical Reports Server (NTRS)
Minier, Elizabeth A.; Suit, William T.
1988-01-01
Various transition methods are used here to study the viscous effects encountered in low density, hypersonic flight, through the transition from free molecular to continuum flow. Methods utilizing Viking data, Shuttle Orbiter data, a Potter number parameter, and a Shock Reynolds number were implemented in the Program to Optimize Simulated Trajectories (POST). Simulations of the Aeroassist Flight Experiment (AFE) using open loop guidance were used to assess the aerodynamic performance of the vehicle. A bank angle was found for each transition method that would result in a 200 nautical-mile apogee. Once this was done, the open loop guidance was replaced by the proposed guidance algorithm for the AFE. Simulations were again conducted using that guidance and the different transitions for comparison. For the gains used, the guidance system showed some sensitivity in apogee altitude to the transition method assumed, but the guidance was able to successfully complete the mission.
NASA Astrophysics Data System (ADS)
Mayo, L. A.; Odenwald, S. F.
2002-09-01
December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the astronomical unit, calculation of longitudes on the earth, and detection of Venus' atmosphere. The NASA Sun Earth Connection Education Forum in partnership with the Solar System Exploration Forum, DPS, and a number of NASA space missions is developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.
Improving Upon String Methods for Transition State Discovery.
Chaffey-Millar, Hugh; Nikodem, Astrid; Matveev, Alexei V; Krüger, Sven; Rösch, Notker
2012-02-14
Transition state discovery via application of string methods has been researched on two fronts. The first front involves development of a new string method, named the Searching String method, while the second one aims at estimating transition states from a discretized reaction path. The Searching String method has been benchmarked against a number of previously existing string methods and the Nudged Elastic Band method. The developed methods have led to a reduction in the number of gradient calls required to optimize a transition state, as compared to existing methods. The Searching String method reported here places new beads on a reaction pathway at the midpoint between existing beads, such that the resolution of the path discretization in the region containing the transition state grows exponentially with the number of beads. This approach leads to favorable convergence behavior and generates more accurate estimates of transition states from which convergence to the final transition states occurs more readily. Several techniques for generating improved estimates of transition states from a converged string or nudged elastic band have been developed and benchmarked on 13 chemical test cases. Optimization approaches for string methods, and pitfalls therein, are discussed.
Measuring stellar granulation during planet transits
NASA Astrophysics Data System (ADS)
Chiavassa, A.; Caldas, A.; Selsis, F.; Leconte, J.; Von Paris, P.; Bordé, P.; Magic, Z.; Collet, R.; Asplund, M.
2017-01-01
Context. Stellar activity and convection-related surface structures might cause bias in planet detection and characterization that use these transits. Surface convection simulations help to quantify the granulation signal. Aims: We used realistic three-dimensional (3D) radiative hydrodynamical (RHD) simulations from the Stagger grid and synthetic images computed with the radiative transfer code Optim3D to model the transits of three prototype planets: a hot Jupiter, a hot Neptune, and a terrestrial planet. Methods: We computed intensity maps from RHD simulations of the Sun and a K-dwarf star at different wavelength bands from optical to far-infrared that cover the range of several ground- and space-based telescopes which observe exoplanet transits. We modeled the transit using synthetic stellar-disk images obtained with a spherical-tile imaging method and emulated the temporal variation of the granulation intensity generating random images covering a granulation time-series of 13.3 h. We measured the contribution of the stellar granulation on the light curves during the planet transit. Results: We identified two types of granulation noise that act simultaneously during the planet transit: (i) the intrinsic change in the granulation pattern with timescale (e.g., 10 min for solar-type stars assumed in this work) is smaller than the usual planet transit ( hours as in our prototype cases); and (ii) the fact that the transiting planet occults isolated regions of the photosphere that differ in local surface brightness as a result of convective-related surface structures. First, we showed that our modeling approach returns granulation timescale fluctuations that are comparable with what has been observed for the Sun. Then, our statistical approach shows that the granulation pattern of solar and K-dwarf-type stars have a non-negligible effect of the light curve depth during the transit, and, consequentially on the determination of the planet transit parameters such as the
NASA Astrophysics Data System (ADS)
Dassoulas, John; McNutt, Ralph L.
2007-01-01
Transit, the US Navy's Navigation Satellite System was conceived at the Applied Physics Laboratory in 1957 by observing the Doppler shift while tracking Sputnik I. As spacecraft development proceeded there was concern about the ability of batteries to maintain the hermetic seal over a 5-year operational life requirement; therefore, alternate energy sources were investigated. The radioisotope thermoelectric generator (RTG) concept was pursued and resulted in the launch of SNAP 3s, providing partial power on both Transit 4A and 4B. SNAP 9s provided full power on three Transit 5BNs. All launches occurred in the early 1960s. When the U.S. conducted the high altitude nuclear test from Johnson Island, several spacecraft were lost due to artificial enhancement of charged particles in the Earth's magnetosphere resulting in rapid degradation of solar cell power production. This led to the decision to have both an RTG and Solar cell/battery design for Transit power systems; hence, a new RTG design, with a separable heat source and radiative coupling to the thermoelectric elements, was flown on TRIAD. This pioneering effort provided the impetus for future RTGs on interplanetary spacecraft. This paper describes the origin and purpose of the Transit program and provides details on the five satellites in that program that were powered by the first American RTGs used in space. The rationale and some of the challenges inherent in that use are also described.
High Energy Exoplanet Transits
NASA Astrophysics Data System (ADS)
Llama, Joe; Shkolnik, Evgenya L.
2017-10-01
X-ray and ultraviolet transits of exoplanets allow us to probe the atmospheres of these worlds. High energy transits have been shown to be deeper but also more variable than in the optical. By simulating exoplanet transits using high-energy observations of the Sun, we can test the limits of our ability to accurately measure the properties of these planets in the presence of stellar activity. We use both disk-resolved images of the Solar disk spanning soft X-rays, the ultraviolet, and the optical and also disk-integrated Sun-as-a-star observations of the Lyα irradiance to simulate transits over a wide wavelength range. We find that for stars with activity levels similar to the Sun, the planet-to-star radius ratio can be overestimated by up to 50% if the planet occults an active region at high energies. We also compare our simulations to high energy transits of WASP-12b, HD 189733, 55 Cnc b, and GJ 436b.
Coale, A J
1984-01-01
Demographic transition is a set of changes in reproductive behavior that are experienced as a society is transformed from a traditional pre-industrial state to a highly developed, modernized structure. The transformation is the substitution of slow growth achieved with low fertility and mortality for slow growth maintained with relatively high fertility and mortality rates. Contrary to early descriptions of the transition, fertility in pre-modern societies was well below the maximum that might be attained. However, it was kept at moderate levels by customs (such as late marriage or prolonged breastfeeding) not related to the number of children already born. Fertility has been reduced during the demographic transition by the adoption of contraception as a deliberate means of avoiding additional births. An extensive study of the transition in Europe shows the absence of a simple link of fertility with education, proportion urban, infant mortality and other aspects of development. It also suggests the importance of such cultural factors as common customs associated with a common language, and the strength of religious traditions. Sufficient modernization nevertheless seems always to bring the transition to low fertility and mortality.
Perspective: The glass transition
NASA Astrophysics Data System (ADS)
Biroli, Giulio; Garrahan, Juan P.
2013-03-01
We provide here a brief perspective on the glass transition field. It is an assessment, written from the point of view of theory, of where the field is and where it seems to be heading. We first give an overview of the main phenomenological characteristics, or "stylised facts," of the glass transition problem, i.e., the central observations that a theory of the physics of glass formation should aim to explain in a unified manner. We describe recent developments, with a particular focus on real space properties, including dynamical heterogeneity and facilitation, the search for underlying spatial or structural correlations, and the relation between the thermal glass transition and athermal jamming. We then discuss briefly how competing theories of the glass transition have adapted and evolved to account for such real space issues. We consider in detail two conceptual and methodological approaches put forward recently, that aim to access the fundamental critical phenomenon underlying the glass transition, be it thermodynamic or dynamic in origin, by means of biasing of ensembles, of configurations in the thermodynamic case, or of trajectories in the dynamic case. We end with a short outlook.
Examining hydrogen transitions.
Plotkin, S. E.; Energy Systems
2007-03-01
This report describes the results of an effort to identify key analytic issues associated with modeling a transition to hydrogen as a fuel for light duty vehicles, and using insights gained from this effort to suggest ways to improve ongoing modeling efforts. The study reported on here examined multiple hydrogen scenarios reported in the literature, identified modeling issues associated with those scenario analyses, and examined three DOE-sponsored hydrogen transition models in the context of those modeling issues. The three hydrogen transition models are HyTrans (contractor: Oak Ridge National Laboratory), MARKAL/DOE* (Brookhaven National Laboratory), and NEMS-H2 (OnLocation, Inc). The goals of these models are (1) to help DOE improve its R&D effort by identifying key technology and other roadblocks to a transition and testing its technical program goals to determine whether they are likely to lead to the market success of hydrogen technologies, (2) to evaluate alternative policies to promote a transition, and (3) to estimate the costs and benefits of alternative pathways to hydrogen development.
NASA Astrophysics Data System (ADS)
Chen, Zhi; Yu, Clare C.
2006-03-01
Noise is present in many physical systems and is often viewed as a nuisance. Yet it can also be a probe of microscopic fluctuations. There have been indications recently that the noise in the resistivity increases in the vicinity of the metal-insulator transition. But what are the characteristics of the noise associated with well-understood first and second order phase transitions? It is well known that critical fluctuations are associated with second order phase transitions, but do these fluctuations lead to enhanced noise? We have addressed these questions using Monte Carlo simulations to study the noise in the 2D Ising model which undergoes a second order phase transition, and in the 5-state Potts model which undergoes a first order phase transition. We monitor these systems as the temperature drops below the critical temperature. At each temperature, after equilibration is established, we obtain the time series of quantities characterizing the properties of the system, i.e., the energy and magnetization per site. We apply different methods, such as the noise power spectrum, the Detrended Fluctuation Analysis (DFA) and the second spectrum of the noise, to analyze the fluctuations in these quantities.
Zhang, Xiao-Jie; Liu, Zhi-Pan
2015-10-13
To identify the low energy pathway for solid-to-solid phase transition has been a great challenge in physics and material science. This work develops a new theoretical method, namely, variable-cell double-ended surface walking (VC-DESW) to locate the transition state (TS) and deduce the pathway in solid phase transition. Inherited from the DESW method ( J. Chem. Theory Comput. 2013 , 9 , 5745 ) for molecular systems, the VC-DESW method implements an efficient mechanism to couple the lattice and atom degrees of freedom. The method features with fast pseudopathway building and accurate TS location for solid phase transition systems without requiring expensive Hessian computation and iterative pathway optimization. A generalized coordinate, consisting of the lattice vectors and the scaled atomic coordinates, is designed for describing the crystal potential energy surface (PES), which is able to capture the anisotropic behavior in phase transition. By comparing with the existing method for solid phase transition in different systems, we show that the VC-DESW method can be much more efficient for finding the TS in crystal phase transition. With the combination of the recently developed unbiased stochastic surface walking pathway sampling method, the VC-DESW is further utilized to resolve the lowest energy pathway of SiO2 α-quartz to quartz-II phase transition from many likely reaction pathways. These new methods provide a powerful platform for understanding and predicting the solid phase transition mechanism and kinetics.
The Concept of Transition System
ERIC Educational Resources Information Center
Raffe, David
2008-01-01
The term "transition system" describes features of a country's institutional arrangements which shape young people's education-work transitions. It explains why national differences in transition processes and outcomes persist despite apparent pressures for convergence. This paper asks how the concept of transition system has been…
Adaptation and optimization of biological transport networks.
Hu, Dan; Cai, David
2013-09-27
It has been hypothesized that topological structures of biological transport networks are consequences of energy optimization. Motivated by experimental observation, we propose that adaptation dynamics may underlie this optimization. In contrast to the global nature of optimization, our adaptation dynamics responds only to local information and can naturally incorporate fluctuations in flow distributions. The adaptation dynamics minimizes the global energy consumption to produce optimal networks, which may possess hierarchical loop structures in the presence of strong fluctuations in flow distribution. We further show that there may exist a new phase transition as there is a critical open probability of sinks, above which there are only trees for network structures whereas below which loops begin to emerge.
Navajo childbirth in transition.
Waxman, A G
1990-03-01
For the Navajo Indians, the transition from home-centered childbearing practices based on religious ritual to biomedically directed childbirth in hospitals was completed over a relatively short time in the middle decades of this century. For Anglo-American society, the acceptance of medically oriented childbirth occurred during an equally short period earlier in the century. The transition was driven for both by many common factors. For Navajo women it was additionally influenced by the social and economic changes that affected the Reservation following the beginning of the Second World War. This paper examines the changes in Navajo childbearing practices and, for comparison, those of the dominant American society. It reviews factors that permitted the acceptance of biomedical childbirth by Navajo women and explores the health implications of the transition.
Quantum interface unbinding transitions
NASA Astrophysics Data System (ADS)
Jakubczyk, P.
2012-08-01
We consider interfacial phenomena accompanying bulk quantum phase transitions in the presence of surface fields. On general grounds we argue that the surface contribution to the system free energy involves a line of singularities characteristic of an interfacial phase transition, occurring below the bulk transition temperature Tc down to T=0. This implies the occurrence of an interfacial quantum critical regime extending into finite temperatures and located within the portion of the phase diagram where the bulk is ordered. Even in situations where the bulk order sets in discontinuously at T=0, the system's behavior at the boundary may be controlled by a divergent length scale if the tricritical temperature is sufficiently low. Relying on an effective interfacial model we compute the surface phase diagram in bulk spatial dimensionality d⩾2 and extract the values of the exponents describing the interfacial singularities in d⩾3.
Transition and laminar instability
NASA Technical Reports Server (NTRS)
Mack, L. M.
1977-01-01
The linear stability theory was applied to the problem of boundary layer transition in incompressible flow. The theory was put into a form suitable for three-dimensional boundary layers; both the temporal and spatial theories were examined; and a generalized Gaster relation for three-dimensional boundary layers was derived. Numerical examples include the stability characteristics of Falkner-Skan boundary layers, the accuracy of the two-dimensional Gaster relation for these boundary layers, and the magnitude and direction of the group velocity for oblique waves in the Blasius boundary layer. Available experiments which bear on the validity of stability theory and its relation to transition are reviewed and the stability theory is applied to transition prediction. The amplitude method is described in which the wide band disturbance amplitude in the boundary layer is estimated from stability theory and an interaction relation for the initial amplitude density of the most unstable frequency.
Anderson, G.W.
1991-09-16
An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l_angle}{phi}{r_angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l_angle}{phi}{r_angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l_angle}{phi}{r_angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l_angle}{phi}{r_angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l_angle}{phi}{r_angle} = 246 GeV unstable. The requirement that the state {l_angle}{phi}{r_angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.
Anderson, G.W.
1991-09-16
An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the state {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.
UTM: Universal Transit Modeller
NASA Astrophysics Data System (ADS)
Deeg, Hans J.
2014-12-01
The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.
Stellar Variability Effects on Transit Spectroscopy
NASA Astrophysics Data System (ADS)
Zellem, Robert Thomas; Swain, Mark R.; Shkolnik, Evgenya; Line, Michael R.; Llama, Joe
2016-10-01
Stellar variability caused by surface magnetic activity poses a great challenge to accurately and precisely characterize the atmospheres of transiting exoplanets. We present a preliminary analysis of the effects of unocculted star spots at IR wavelengths on planetary transmission and emission spectra. We will explore how stellar variability changes the derived exoplanet atmospheric parameters inferred through retrievals for a group of exoplanetary hosts stars. Our study includes stars ranging in activity levels from an inactive sun to a very active late-type star, and a range of planetary masses from super-Earths to Jupiters. These effects will be especially important for the high precision measurements (<100 ppm) needed to characterize the atmospheric composition of smaller planets. This work is critical for optimizing the exoplanet observing program of JWST, which will study known habitable zone transiting planets as well as new ones found by TESS orbiting nearby M dwarfs, which are more active than solar-type stars.
Sequence Compaction to Preserve Transition Frequencies
Pinar, Ali; Liu, C.L.
2002-12-12
Simulation-based power estimation is commonly used for its high accuracy despite excessive computation times. Techniques have been proposed to speed it up by compacting an input sequence while preserving its power-consumption characteristics. We propose a novel method to compact a sequence that preserves transition frequencies. We prove the problem is NP-Complete, and propose a graph model to reduce it to that of finding a heaviest weighted trail on a directed graph, along with a heuristic utilizing this model. We also propose using multiple sequences for better accuracy with even shorter sequences. Experiments showed that power dissipation can be estimated with an error of only 2.3 percent, while simulation times are reduced by 10. Proposed methods effectively preserve transition frequencies and generated solutions that are very close to an optimal. Experiments also showed that multiple sequences granted more accurate results with even shorter sequences.
Optimization of composite structures
NASA Technical Reports Server (NTRS)
Stroud, W. J.
1982-01-01
Structural optimization is introduced and examples which illustrate potential problems associated with optimized structures are presented. Optimized structures may have very low load carrying ability for an off design condition. They tend to have multiple modes of failure occurring simultaneously and can, therefore, be sensitive to imperfections. Because composite materials provide more design variables than do metals, they allow for more refined tailoring and more extensive optimization. As a result, optimized composite structures can be especially susceptible to these problems.
Meta-functional Criteria and School-to-Work Transition.
ERIC Educational Resources Information Center
Tchibozo, Guy
2002-01-01
Uses a microeconomic model to explain behavior of actors in school-to-work transition that proposes optimal strategies and explains causes of failure. Suggests that metafunctional criteria (personality, behavior, employment stability, productivity, adaptability, social involvement) are crucial factors in recruitment decisions. (Contains 56…
Transition and the Education of the New South African Citizen
ERIC Educational Resources Information Center
Hammett, Daniel; Staeheli, Lynn
2013-01-01
South Africa's democratic transition was a time of optimism, with immense hopes pinned on the youth who would be educated to see themselves as equal citizens. It was also a time of pragmatic decision making, not least in the education sector, which would shape the future of the country. Negotiating the imperatives of redress, development, and…
Topic Transition in Educational Videos Using Visually Salient Words
ERIC Educational Resources Information Center
Gandhi, Ankit; Biswas, Arijit; Deshmukh, Om
2015-01-01
In this paper, we propose a visual saliency algorithm for automatically finding the topic transition points in an educational video. First, we propose a method for assigning a saliency score to each word extracted from an educational video. We design several mid-level features that are indicative of visual saliency. The optimal feature combination…
Radiation Shielding Optimization on Mars
NASA Technical Reports Server (NTRS)
Slaba, Tony C.; Mertens, Chris J.; Blattnig, Steve R.
2013-01-01
Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.
Optimal control of overdamped systems
NASA Astrophysics Data System (ADS)
Zulkowski, Patrick R.; DeWeese, Michael R.
2015-09-01
Nonequilibrium physics encompasses a broad range of natural and synthetic small-scale systems. Optimizing transitions of such systems will be crucial for the development of nanoscale technologies and may reveal the physical principles underlying biological processes at the molecular level. Recent work has demonstrated that when a thermodynamic system is driven away from equilibrium then the space of controllable parameters has a Riemannian geometry induced by a generalized inverse diffusion tensor. We derive a simple, compact expression for the inverse diffusion tensor that depends solely on equilibrium information for a broad class of potentials. We use this formula to compute the minimal dissipation for two model systems relevant to small-scale information processing and biological molecular motors. In the first model, we optimally erase a single classical bit of information modeled by an overdamped particle in a smooth double-well potential. In the second model, we find the minimal dissipation of a simple molecular motor model coupled to an optical trap. In both models, we find that the minimal dissipation for the optimal protocol of duration τ is proportional to 1 /τ , as expected, though the dissipation for the erasure model takes a different form than what we found previously for a similar system.
Nursing Role Transition Preceptorship
ERIC Educational Resources Information Center
Batory, Susan M.
2014-01-01
The preceptorship clinical experience in a practical nursing (PN) program at a Midwestern community college is considered crucial to the PN students' transition from novice nurse to professional nurse. However, no research has been available to determine whether the preceptorship clinical accomplishes its purpose. A case study was conducted to…
ERIC Educational Resources Information Center
Bundy, Michael L., Ed.; Gumaer, James, Ed.
1984-01-01
Focuses on disrupted families and the role of the school counselor in helping children adjust. Describes characteristics of healthy families, and discusses the transition to the blended family, effects of divorce groups on children's classroom behavior, counseling children in stepfamilies, single-parent families, and parenting strengths of single…
ERIC Educational Resources Information Center
Varmecky, Jane Hyde
2012-01-01
Many adults return to formal learning situations to pursue lifelong learning goals because their lives are in transition from dealing with real-life problems such as divorce and re-marriage. The purpose of this study was to describe what couples learned that contributed to the success of their subsequent marriages and how they learned it. The…
Immigration and Adult Transitions
ERIC Educational Resources Information Center
Rumbaut, Ruben G.; Komaie, Golnaz
2010-01-01
Almost 30 percent of the more than 68 million young adults aged eighteen to thirty-four in the United States today are either foreign born or of foreign parentage. As these newcomers make their transitions to adulthood, say Ruben Rumbaut and Golnaz Komaie, they differ significantly not only from one another but also from their native-parentage…
The contact percolation transition
NASA Astrophysics Data System (ADS)
Shen, Tianqi; O'Hern, Corey; Shattuck, Mark
2012-02-01
Typical quasistatic compression algorithms for generating jammed packings of athermal, purely repulsive particles begin with dilute configurations and then apply successive compressions with relaxation of the elastic energy allowed between each compression step. It is well-known that during isotropic compression athermal systems with purely repulsive interactions undergo a jamming transition at packing fraction φJ from an unjammed state with zero pressure to a jammed, rigid state with nonzero pressure. Using extensive computer simulations, we show that a novel second-order-like, contact percolation, which signals the formation of a system-spanning cluster of mutually contacting particles, occurs at φP< φJ, preceding the jamming transition. By measuring the number of non-floppy modes of the dynamical matrix, the displacement field between successive compression steps, and the overlap between the adjacency matrix, which represents the network of contacting grains, at φ and φJ, we find that the contact percolation transition also heralds the onset of nontrivial response to applied stress. Highly heterogeneous, cooperative, and non-affine particle motion occurs in unjammed systems significantly below the jamming transition for φP< φ< φJ,
NASA Astrophysics Data System (ADS)
Kipping, D. M.; Torres, G.; Henze, C.; Teachey, A.; Isaacson, H.; Petigura, E.; Marcy, G. W.; Buchhave, L. A.; Chen, J.; Bryson, S. T.; Sandford, E.
2016-04-01
Decadal-long radial velocity surveys have recently started to discover analogs to the most influential planet of our solar system, Jupiter. Detecting and characterizing these worlds is expected to shape our understanding of our uniqueness in the cosmos. Despite the great successes of recent transit surveys, Jupiter analogs represent a terra incognita, owing to the strong intrinsic bias of this method against long orbital periods. We here report on the first validated transiting Jupiter analog, Kepler-167e (KOI-490.02), discovered using Kepler archival photometry orbiting the K4-dwarf KIC-3239945. With a radius of (0.91+/- 0.02) {R}{{J}}, a low orbital eccentricity ({0.06}-0.04+0.10), and an equilibrium temperature of (131+/- 3) K, Kepler-167e bears many of the basic hallmarks of Jupiter. Kepler-167e is accompanied by three Super-Earths on compact orbits, which we also validate, leaving a large cavity of transiting worlds around the habitable-zone. With two transits and continuous photometric coverage, we are able to uniquely and precisely measure the orbital period of this post snow-line planet (1071.2323 ± 0.0006d), paving the way for follow-up of this K = 11.8 mag target.
Military Lives: Coaching Transitions
ERIC Educational Resources Information Center
Beech, Nick; Gold, Jeff; Beech, Susan
2017-01-01
Purpose: The purpose of this paper is to first consider how veterans use talk to shape interpretations of personal and social identity. Second, this paper seeks to gain an understanding of how veterans see themselves in a civilian world, their ability to re-conceptualise and realign their perspective on life to support their transition in to a…
String mediated phase transitions
NASA Technical Reports Server (NTRS)
Copeland, ED; Haws, D.; Rivers, R.; Holbraad, S.
1988-01-01
It is demonstrated from first principles how the existence of string-like structures can cause a system to undergo a phase transition. In particular, the role of topologically stable cosmic string in the restoration of spontaneously broken symmetries is emphasized. How the thermodynamic properties of strings alter when stiffness and nearest neighbor string-string interactions are included is discussed.
Variational transition state theory
Truhlar, D.G.
1993-12-01
This research program involves the development of variational transition state theory (VTST) and semiclassical tunneling methods for the calculation of gas-phase reaction rates and selected applications. The applications are selected for their fundamental interest and/or their relevance to combustion.
ERIC Educational Resources Information Center
Kellems, Ryan O.; Morningstar, Mary E.
2010-01-01
The Individuals With Disabilities Education Improvement Act of 2004 (IDEA) states that transition planning should begin at the earliest age appropriate and no later than age 16. IDEA requires schools to make collaborative efforts to provide students access to an array of postschool activities including integrated employment, postsecondary…
exorings: Exoring Transit Properties
NASA Astrophysics Data System (ADS)
Zuluaga, Jorge I.; Kipping, David M.; Sucerquia, Mario; Alvarado, Jaime A.
2017-03-01
Exorings is suitable for surveying entire catalogs of transiting planet candidates for exoring candidates, providing a subset of objects worthy of more detailed light curve analysis. Moreover, it is highly suited for uncovering evidence of a population of ringed planets by comparing the radius anomaly and PR-effects in ensemble studies.
ERIC Educational Resources Information Center
Britton, Patti O., Ed.; McGee, Michael, Ed.
1987-01-01
This issue of "Emphasis" deals with families in transition, providing some model programs for the new family and some historical perspectives on how families have developed over time. Articles include: (1) "Nostalgia on the Right" (Nancy Theriot); (2) "Heart to Heart" (Nancy Harrington-MacLennan); (3) "The Media Get the Message" (Janet Alyn); (4)…
Outplacement as Transition Counseling.
ERIC Educational Resources Information Center
Mirabile, Richard J.
1985-01-01
Describes outplacement counseling as a process that enables management to deal with the problem of the employee who must be released or the staff that must be reduced. Discusses the process of outplacement counseling, the stages of transition counseling, and techniques to be implemented. (BH)
ERIC Educational Resources Information Center
Office of the Assistant Secretary of Defense for Manpower and Reserve Affairs (DOD), Washington, DC.
Operated on a voluntary, decentralized basis at 215 military bases (58 overseas), the TRANSITION Program is designed to provide maximum guidance and training or educational opportunities for servicemen during their last six months of duty to prepare them for productive reentry into civilian life. Public and private placement services are also…
ERIC Educational Resources Information Center
Johnston, William; McAllister, Alex M.
2012-01-01
Successful outcomes for a "Transition Course in Mathematics" have resulted from two unique design features. The first is to run the course as a "survey course" in mathematics, introducing sophomore-level students to a broad set of mathematical fields. In this single mathematics course, undergraduates benefit from an introduction of proof…
Structural transitions in clusters
NASA Astrophysics Data System (ADS)
Ghazali, A.; Lévy, J.-C. S.
1997-02-01
Monatomic clusters are studied by Monte Carlo relaxation using generalized Lennard-Jones potentials. A transition from an icosahedral symmetry to a crystalline symmetry with stacking faults is always observed. Bcc-based soft atom clusters are found to have a lower energy than the corresponding hcp and fcc ones below the melting point.
Transitions in Higher Education
ERIC Educational Resources Information Center
Hussey, Trevor; Smith, Patrick
2010-01-01
This paper offers ideas towards a solution of some of the problems that arise due to the extension of higher education to an ever wider range of students: especially student drop-out. It suggests that, as far as is practical, the design and delivery of higher education should be based upon the major changes or transitions which the students…
ERIC Educational Resources Information Center
Johnston, William; McAllister, Alex M.
2012-01-01
Successful outcomes for a "Transition Course in Mathematics" have resulted from two unique design features. The first is to run the course as a "survey course" in mathematics, introducing sophomore-level students to a broad set of mathematical fields. In this single mathematics course, undergraduates benefit from an introduction of proof…
Singing Smoothes Classroom Transitions
ERIC Educational Resources Information Center
Mathews, Sarah E.
2012-01-01
Just as humming a merry tune helped Snow White and her furry animal friends to quickly clean a filthy cottage in the movie "Snow White and the Seven Dwarfs" (Disney & Cottrell, 1937), singing can be an effective way to help keep young children fully engaged during classroom transitions. The purposes of this article are to: (1) consider why…
Modeling of transitional flows
NASA Technical Reports Server (NTRS)
Lund, Thomas S.
1988-01-01
An effort directed at developing improved transitional models was initiated. The focus of this work was concentrated on the critical assessment of a popular existing transitional model developed by McDonald and Fish in 1972. The objective of this effort was to identify the shortcomings of the McDonald-Fish model and to use the insights gained to suggest modifications or alterations of the basic model. In order to evaluate the transitional model, a compressible boundary layer code was required. Accordingly, a two-dimensional compressible boundary layer code was developed. The program was based on a three-point fully implicit finite difference algorithm where the equations were solved in an uncoupled manner with second order extrapolation used to evaluate the non-linear coefficients. Iteration was offered as an option if the extrapolation error could not be tolerated. The differencing scheme was arranged to be second order in both spatial directions on an arbitrarily stretched mesh. A variety of boundary condition options were implemented including specification of an external pressure gradient, specification of a wall temperature distribution, and specification of an external temperature distribution. Overall the results of the initial phase of this work indicate that the McDonald-Fish model does a poor job at predicting the details of the turbulent flow structure during the transition region.
ERIC Educational Resources Information Center
Environmental Science and Technology, 1975
1975-01-01
Mass transit is possible in the United States, but only if the form it takes offers americans the quality of ride--cheap, private and rapid--they now have in the automobile. If these criteria are not achieved, Americans will continue to drive. (BT)
Nursing Role Transition Preceptorship
ERIC Educational Resources Information Center
Batory, Susan M.
2014-01-01
The preceptorship clinical experience in a practical nursing (PN) program at a Midwestern community college is considered crucial to the PN students' transition from novice nurse to professional nurse. However, no research has been available to determine whether the preceptorship clinical accomplishes its purpose. A case study was conducted to…
ERIC Educational Resources Information Center
Sargent, Alice G.; Schlossberg, Nancy K.
1988-01-01
Suggests basic truths about adult behavior: (1) adult behavior is determined by transition, not age; (2) adults are motivated to learn and change by a need to control, belong, matter, master, renew, and take stock; and (3) adult readiness for change depends on situation, support, self, and strategies. (JOW)
2017-09-27
Transit of Venus as seen at 762nm in the CO Module. This image is from NASA Astronaut Don Petttit shot from onboard the International Space Station on June 5, 2012. Petttit, who had the foresight to bring a solar filter for his camera, will be capturing the June 5 Venus Transit from the International Space Station with the images downloading in almost real-time. He will photograph through the European Space Agency-built "cupola", removing the scratch panes to get crisp, clear images. Credit: NASA To read more about the 2012 Venus Transit go to: sunearthday.nasa.gov/transitofvenus Add your photos of the Transit of Venus to our Flickr Group here: www.flickr.com/groups/venustransit/ NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
2012-09-19
Mars has two small, asteroid-sized moons named Phobos and Deimos. This frame from an animation shows the point of view of the rover, located near the equator of Mars, as these moons occasionally pass in front of, or transit, the disk of the sun.
ERIC Educational Resources Information Center
Timpane, Michael; And Others
A study team was commissioned to critically review three independent reports on youth and schooling: "Youth: Transition to Adulthood"; "The Education of Adolescents"; and "The Reform of Secondary Education." The study team examined the reports in light of the most recent available social science evidence. The three reports, presenting similar…
Singing Smoothes Classroom Transitions
ERIC Educational Resources Information Center
Mathews, Sarah E.
2012-01-01
Just as humming a merry tune helped Snow White and her furry animal friends to quickly clean a filthy cottage in the movie "Snow White and the Seven Dwarfs" (Disney & Cottrell, 1937), singing can be an effective way to help keep young children fully engaged during classroom transitions. The purposes of this article are to: (1) consider why…
ERIC Educational Resources Information Center
Sherman, Jill Z.; Osborn, Sandra R.
Vocationally at-risk students have one or a combination of handicaps affecting mobility, coordination, communication, self-care and/or cognition which may significantly interfere with the goals of successful student-to-adult transition, namely employment, productive work, and independent community living. A program for students with physical…
Transition Path Sampling Methods
NASA Astrophysics Data System (ADS)
Dellago, C.; Bolhuis, P. G.; Geissler, P. L.
Transition path sampling, based on a statistical mechanics in trajectory space, is a set of computational methods for the simulation of rare events in complex systems. In this chapter we give an overview of these techniques and describe their statistical mechanical basis as well as their application.
Administrative Theory in Transition.
ERIC Educational Resources Information Center
Griffiths, Daniel E.
This monograph analyzes transition in educational administrative theory. A brief introductory section describes the theoretical movement, the substance and repercussions of Thomas Greenfield's critique of educational administrative theory in 1974, and emerging qualitative approaches. Seven readings, all written by the volume's author, view…
Selected Readings in Transition.
ERIC Educational Resources Information Center
Harnisch, Delwyn L.; And Others
This collection of readings covers critical issues related to transition of youth with disabilities from school to post-school experiences. The first paper, titled "'Cognitive Return' of Schooling for Students with Disabilities: Preliminary Findings from 'High School and Beyond'" by Delwyn L. Harnisch and Ian A. G. Wilkinson, applies…
Transition at hypersonic speeds
NASA Technical Reports Server (NTRS)
Morkovin, Mark V.
1987-01-01
Certain conjectures on the physics of instabilities in high-speed flows are discussed and the state of knowledge of hypersonic transition summarized. The case is made for an unpressured systematic research program in this area consisting of controlled microscopic experiments, theory, and numerical simulations.
Electrothermal design aspects of transitioning solid armatures
NASA Astrophysics Data System (ADS)
Schoolderman, A. J.; de Zeeuw, W. A.; Koops, M.
1993-01-01
To optimize erosion-free rail accelerator launch of solid brush armatures, a 2D model and an analytical model are used to study the temperature distribution, the coefficient of friction and the transitioning behavior of U-shaped solid armatures made of Cu, Al, Mo, and Ti during electromagnetic launch. In order to experimentally verify the insights gained from these theoretical studies, recently developed diagnostics are applied. The growth potential of solid armatures for weapons applications is highlighted by considering such materials as Ti and Mo.
NASA Technical Reports Server (NTRS)
Doyle, Laurance R.
1998-01-01
During the past five years we have pursued the detection of extrasolar planets by the photometric transit method, i.e. the detection of a planet by watching for a drop in the brightness of the light as it crosses in front of a star. The planetary orbit must cross the line-of-sight and so most systems will not be lined up for such a transit to ever occur. However, we have looked at eclipsing binary systems which are already edge-on. Such systems must be very small in size as this makes the differential light change due to a transit much greater for a given planet size (the brightness difference will be proportional to the area of the transiting planet to the disc area of the star). Also, the planet forming region should be closer to the star as small stars are generally less luminous (that is, if the same thermal regime for planet formation applies as in the solar system). This led to studies of the habitable zone around other stars, as well. Finally, we discovered that our data could be used to detect giant planets without transits as we had been carefully timing the eclipses of the stars (using a GPS antenna for time) and this will drift by being offset by any giant planets orbiting around the system, as well. The best summary of our work may be to just summarize the 21 refereed papers produced during the time of this grant. This will be done is chronological order and in each section separately.
Quantum Transition State Theory
NASA Astrophysics Data System (ADS)
Waalkens, Holger
2009-03-01
The main idea of Wigner's transition state theory (TST) is to compute reaction rates from the flux through a dividing surface placed between reactants and products. In order not to overestimate the rate the dividing surface needs to have the no- recrossing property, i.e. reactive trajectories cross the dividing surface exactly once, and nonreactive trajectories do not cross it at all. The long standing problem of how to construct such a diving surface for multi-degree-of-freedom systems was solved only recently using ideas from dynamical systems theory. Here a normal form allows for a local decoupling of the classical dynamics which leads to the explicit construction of the phase space structures that govern the reaction dynamics through transition states. The dividing surface is spanned by a normally hyperbolic manifold which is the mathematical manifestation of the transition state as an unstable invariant subsystem of one degree of freedom less than the full system. The mere existence of a quantum version of TST is discussed controversially in the literature. The key isssue is the presence of quantum mechanical tunneling which prohibits the existence of a local theory analogous to the classical case. Various approaches have been devloped to overcome this problem by propagating quantum wavefunctions through the transition state region. These approaches have in common that they are computationally very expensive which seriously limits their applicability. In contrast the approach by Roman Schubert, Stephen Wiggins and myself is local in nature. A quantum normal form allows us to locally decouple the quantum dynamics to any desired order in Planck's constant. This yields not only the location of the scattering and resonance wavefunctions relative to the classical phase space structures, but also leads to very efficient algorithms to compute cumulative reaction probabilities and Gamov-Siegert resonances which are the quantum imprints of the transition state.
Water's second glass transition.
Amann-Winkel, Katrin; Gainaru, Catalin; Handle, Philip H; Seidl, Markus; Nelson, Helge; Böhmer, Roland; Loerting, Thomas
2013-10-29
The glassy states of water are of common interest as the majority of H2O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water's calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This "double Tg scenario" is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at Tg,2 about five times as large as at Tg,1. By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate-dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20-25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known ("superstrong"), and also high-density liquid is classified as a strong liquid.
Control of rare events in reaction and population systems by deterministically imposed transitions.
Khasin, M; Dykman, M I
2011-03-01
We consider control of reaction and population systems by imposing transitions between states with different numbers of particles or individuals. The transitions take place at predetermined instants of time. Even where they are significantly less frequent than spontaneous transitions, they can exponentially strongly modify the rates of rare events, including switching between metastable states or population extinction. We also study optimal control of rare events. Specifically, we are interested in the optimal control of disease extinction for a limited vaccine supply. A comparison is made with control of rare events by modulating the rates of elementary transitions rather than imposing transitions deterministically. It is found that, unexpectedly, for the same mean control parameters, controlling the transitions rates can be more efficient.
Jeon, Haram; Salinas, Daniel; Baker, David P
2015-12-01
Previous studies found that developed and developing countries present opposite education-overweight gradients but have not considered the dynamics at different levels of national development. An inverted U-shaped curve is hypothesized to best describe the education-overweight association. It is also hypothesized that as the nutrition transition unfolds within nations the shape of education-overweight curve changes. Multilevel logistic regression was used to estimate the moderating effect of the nutrition transition at the population level on the education-overweight gradient. At the individual level, a non-linear estimate of the education association was used to assess the optimal functional form of the association across the nutrition transition. Twenty-two administrations of the Demographic and Health Survey, collected at different time points across the nutrition transition in nine Latin American/Caribbean countries. Mothers of reproductive age (15-49 years) in each administration (n 143 258). In the pooled sample, a non-linear education gradient on mothers' overweight was found; each additional year of schooling increases the probability of being overweight up to the end of primary schooling, after which each additional year of schooling decreases the probability of overweight. Also, as access to diets high in animal fats and sweeteners increases over time, the curve's critical point moves to lower education levels, the detrimental positive effect of education diminishes, and both occur as the overall risk of overweight increases with greater access to harmful diets. Both hypotheses were supported. As the nutrition transition progresses, the education-overweight curve shifts steadily to a negative linear association with a higher average risk of overweight; and education, at increasingly lower levels, acts as a 'social vaccine' against increasing risk of overweight. These empirical patterns fit the general 'population education transition' curve hypothesis
Computational Methods for Design, Control and Optimization
2007-10-01
34scenario" that applies to channel flows ( Poiseuille flows , Couette flow ) and pipe flows . Over the past 75 years many complex "transition theories" have... Simulation of Turbulent Flows , Springer Verlag, 2005. Additional Publications Supported by this Grant 1. J. Borggaard and T. Iliescu, Approximate Deconvolution...rigorous analysis of design algorithms that combine numerical simulation codes, approximate sensitivity calculations and optimization codes. The fundamental
Improving care transitions: current practice and future opportunities for pharmacists.
Hume, Anne L; Kirwin, Jennifer; Bieber, Heather L; Couchenour, Rachel L; Hall, Deanne L; Kennedy, Amy K; LaPointe, Nancy M Allen; Burkhardt, Crystal D O; Schilli, Kathleen; Seaton, Terry; Trujillo, Jennifer; Wiggins, Barbara
2012-11-01
During the past decade, patient safety issues during care transitions have gained greater attention at both the local and national level. Readmission rates to U.S. hospitals are high, often because of poor care transitions. Serious adverse drug events (ADEs) caused by an incomplete understanding of changes in complex drug regimens can be an important factor contributing to readmission rates. This paper describes the roles and responsibilities of pharmacists in ensuring optimal outcomes from drug therapy during care transitions. Barriers to effective care transitions, including inadequate communication, poor care coordination, and the lack of one clinician ultimately responsible for these transitions, are discussed. This paper also identifies specific patient populations at high risk of ADEs during care transitions. Several national initiatives and newer care transition models are discussed, including multi- and interdisciplinary programs with pharmacists as key members. Among their potential roles, pharmacists should participate on medical rounds where available, perform medication reconciliation and admission drug histories, apply their knowledge of drug therapy to anticipate and resolve problems during transitions, communicate changes in drug regimens between providers and care settings, assess the appropriateness and patient understanding of drug regimens, promote adherence, and assess health literacy. In addition, this paper identifies barriers and ongoing challenges limiting greater involvement of pharmacists from different practice settings during care transitions. Professional degree programs and residency training programs should increase their emphasis on pharmacists' roles, especially as part of interdisciplinary teams, in improving patient safety during care transitions in diverse practice settings. This paper also recommends that Accreditation Council for Pharmacy Education (ACPE) standards include specific language regarding the exposure of students to
ERIC Educational Resources Information Center
Kaehne, Axel; Beyer, Stephen
2009-01-01
The paper reports the findings of a study of professionals in strategic and operational positions who were involved in transition planning for young people with learning disabilities. Respondents were asked to comment on what they regarded as the optimal aim and outcome of transition from school to post-school placements. The results illustrate…
A Qualitative Analysis of an Advanced Practice Nurse-Directed Transitional Care Model Intervention
ERIC Educational Resources Information Center
Bradway, Christine; Trotta, Rebecca; Bixby, M. Brian; McPartland, Ellen; Wollman, M. Catherine; Kapustka, Heidi; McCauley, Kathleen; Naylor, Mary D.
2012-01-01
Purpose: The purpose of this study was to describe barriers and facilitators to implementing a transitional care intervention for cognitively impaired older adults and their caregivers lead by advanced practice nurses (APNs). Design and Methods: APNs implemented an evidence-based protocol to optimize transitions from hospital to home. An…
The Mongolia experience: transitioning within transition.
MacKenzie, Richard G
2009-12-01
Although Mongolia has a long and distinguished history, as a new and emerging democracy it is experiencing the pains of transition-one that is moving the country from its pastoral and nomadic past into the 21st century. Confounded by its previous dependence on socialist Soviet Russia, the concept of a market economy seems opportunistic for some, while for those living within the traditional lifestyle of the herdsman in the countryside it is confusing and threatening to family structure and values. Adolescents and young adults are caught at the interface-not only of their own development, but by the disparities between tradition and Western values, new technology, and freedoms granted by the emerging democracy, and by the civic practice of democracy itself. Conceptually the new belongs to the young, and yet limited health and educational resources are available to modulate and focus both threats and opportunities. Using the analogy of the spirit banner of the warrior, it is the young as the warriors of the 21st century who have the energy and investment in the future that will be needed to shepherd this change. Both personal and public health, within the context of development, the psychobiological model, and the political and social ecology will be strong determinants of success. It is a parallel investment in both youth and the ideals they represent that will ensure success for the new Mongolia.
Alternative fuel transit buses: The Pierce Transit Success Story
1996-10-01
The Pierce transit program for operating mass transit buses on compressed natural gas (CNG) is described. Cost, reliability, fuel efficiency, emission of combustion products, and future trends are discussed.
Particle Swarm Optimization Toolbox
NASA Technical Reports Server (NTRS)
Grant, Michael J.
2010-01-01
The Particle Swarm Optimization Toolbox is a library of evolutionary optimization tools developed in the MATLAB environment. The algorithms contained in the library include a genetic algorithm (GA), a single-objective particle swarm optimizer (SOPSO), and a multi-objective particle swarm optimizer (MOPSO). Development focused on both the SOPSO and MOPSO. A GA was included mainly for comparison purposes, and the particle swarm optimizers appeared to perform better for a wide variety of optimization problems. All algorithms are capable of performing unconstrained and constrained optimization. The particle swarm optimizers are capable of performing single and multi-objective optimization. The SOPSO and MOPSO algorithms are based on swarming theory and bird-flocking patterns to search the trade space for the optimal solution or optimal trade in competing objectives. The MOPSO generates Pareto fronts for objectives that are in competition. A GA, based on Darwin evolutionary theory, is also included in the library. The GA consists of individuals that form a population in the design space. The population mates to form offspring at new locations in the design space. These offspring contain traits from both of the parents. The algorithm is based on this combination of traits from parents to hopefully provide an improved solution than either of the original parents. As the algorithm progresses, individuals that hold these optimal traits will emerge as the optimal solutions. Due to the generic design of all optimization algorithms, each algorithm interfaces with a user-supplied objective function. This function serves as a "black-box" to the optimizers in which the only purpose of this function is to evaluate solutions provided by the optimizers. Hence, the user-supplied function can be numerical simulations, analytical functions, etc., since the specific detail of this function is of no concern to the optimizer. These algorithms were originally developed to support entry
Ridzal, Danis
2007-03-01
Aristos is a Trilinos package for nonlinear continuous optimization, based on full-space sequential quadratic programming (SQP) methods. Aristos is specifically designed for the solution of large-scale constrained optimization problems in which the linearized constraint equations require iterative (i.e. inexact) linear solver techniques. Aristos' unique feature is an efficient handling of inexactness in linear system solves. Aristos currently supports the solution of equality-constrained convex and nonconvex optimization problems. It has been used successfully in the area of PDE-constrained optimization, for the solution of nonlinear optimal control, optimal design, and inverse problems.
Assessment for Transitions Planning. PRO-ED Series on Transition.
ERIC Educational Resources Information Center
Clark, Gary M.
Part of a series designed to provide practical resources for transition personnel on a variety of topics essential to the process of preparing individuals with disabilities for adulthood, this guide focuses on assessment for transition planning. Chapter 1, "Transitions Assessment: What Do We Need To Know about Students and Why?," discusses the…
Transitions: exploring the frontier.
Corless, Inge B
End-of-life experiences go by various terms, including near-death experiences (NDEs), death bed visions, death bed phenomena, death bed coincidences, and nearing death awareness. Death bed escorts is the term applied to the vision of deceased family members or friends who inform the dying person that they will be accompanied in the transition from life. In this article, I examine the subject of NDEs and death bed escorts, starting with the rich body of work provided by Robert and Beatrice Kastenbaum. A subject of some interest to Robert Kastenbaum, he explored this frontier in his many writings on dying, death, and bereavement. Ever the pioneer and having made the ultimate transition, he may yet be exploring new frontiers.
High speed transition prediction
NASA Technical Reports Server (NTRS)
Gasperas, Gediminis
1993-01-01
The main objective of this work period was to develop, maintain and exercise state-of-the-art methods for transition prediction in supersonic flow fields. Basic state and stability codes, acquired during the last work period, were exercised and applied to calculate the properties of various flowfields. The development of a code for the prediction of transition location using a currently novel method (the PSE or Parabolized Stability Equation method), initiated during the last work period and continued during the present work period, was cancelled at mid-year for budgetary reasons. Other activities during this period included the presentation of a paper at the APS meeting in Tallahassee, Florida entitled 'Stability of Two-Dimensional Compressible Boundary Layers', as well as the initiation of a paper co-authored with H. Reed of the Arizona State University entitled 'Stability of Boundary Layers'.
Emergence and Phase Transitions
NASA Astrophysics Data System (ADS)
Sikkema, Arnold
2006-05-01
Phase transitions are well defined in physics through concepts such as spontaneous symmetry breaking, order parameter, entropy, and critical exponents. But emergence --- also exhibiting whole-part relations (such as top-down influence), unpredictability, and insensitivity to microscopic detail --- is a loosely-defined concept being used in many disciplines, particularly in psychology, biology, philosophy, as well as in physics[1,2]. I will review the concepts of emergence as used in the various fields and consider the extent to which the methods of phase transitions can clarify the usefulness of the concept of emergence both within the discipline of physics and beyond.1. Robert B. Laughlin, A Different Universe: Reinventing Physics from the Bottom Down (New York: Basic Books, 2005). 2. George F.R. Ellis, ``Physics and the Real World'', Physics Today, vol. 58, no. 7 (July 2005) pp. 49-54.
Internet Protocol Transition Workbook
1982-03-01
i~yif.al Pi.y~iiy wi -! b , ..aye meaning. U [Page il March 1982 Internet Protocol Transition Workbook CONTACTS ARPANET MANAGEMENT. POLICY, AND SERVICE...C) September 1981 Internet Protocol Example 2: In this example, we show fi -st a moderate size internet datagram (452 data octets), then two...00111100. fI Note that the assumed maximum segment lifetime is two minutes. Here we explicitly ask that a segment be destroyed if it cannot be delivered by
Nigeria in Political Transition
2005-06-03
General Sani Abacha, the military leader who took power in Nigeria in 1993, died of a reported heart attack and was replaced by General Abdulsalam...Abubakar. On July 7, 1998, Moshood Abiola, the believed winner of the 1993 presidential election, also died of a heart attack during a meeting with U.S...as the most serious and effective effort in decades. Transition to Civilian Rule Abacha died, reportedly of a heart attack , on June 8, 1998. The
High speed transition prediction
NASA Technical Reports Server (NTRS)
Gasperas, Gediminis
1992-01-01
The main objective of this work period was to develop, acquire and apply state-of-the-art tools for the prediction of transition at high speeds at NASA Ames. Although various stability codes as well as basic state codes were acquired, the development of a new Parabolized Stability Equation (PSE) code was minimal. The time that was initially allocated for development was used on other tasks, in particular for the Leading Edge Suction problem, in acquiring proficiency in various graphics tools, and in applying these tools to evaluate various Navier-Stokes and Euler solutions. The second objective of this work period was to attend the Transition and Turbulence Workshop at NASA Langley in July and August, 1991. A report on the Workshop follows. From July 8, 1991 to August 2, 1991, the author participated in the Transition and Turbulence Workshop at NASA Langley. For purposes of interest here, analysis can be said to consist of solving simplified governing equations by various analytical methods, such as asymptotic methods, or by use of very meager computer resources. From the composition of the various groups at the Workshop, it can be seen that analytical methods are generally more popular in Great Britain than they are in the U.S., possibly due to historical factors and the lack of computer resources. Experimenters at the Workshop were mostly concerned with subsonic flows, and a number of demonstrations were provided, among which were a hot-wire experiment to probe the boundary layer on a rotating disc, a hot-wire rake to map a free shear layer behind a cylinder, and the use of heating strips on a flat plate to control instability waves and consequent transition. A highpoint of the demonstrations was the opportunity to observe the rather noisy 'quiet' supersonic pilot tunnel in operation.
NASA Astrophysics Data System (ADS)
Brekke, P.; Murdin, P.
2000-11-01
Ultraviolet emission lines emitted from the SOLAR TRANSITION REGION are often shifted from their expected rest wavelengths. Shifts of spectral lines are due to the so-called DOPPLER EFFECT, where the source of emission is moving either away from or towards the observer, causing a change in the apparent wavelength. The shifted emission lines are most often interpreted as a flow of plasma along ...
Stimulated coherent transition radiation
Hung-chi Lihn
1996-03-01
Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.
Multidisciplinary Optimization for Aerospace Using Genetic Optimization
NASA Technical Reports Server (NTRS)
Pak, Chan-gi; Hahn, Edward E.; Herrera, Claudia Y.
2007-01-01
In support of the ARMD guidelines NASA's Dryden Flight Research Center is developing a multidisciplinary design and optimization tool This tool will leverage existing tools and practices, and allow the easy integration and adoption of new state-of-the-art software. Optimization has made its way into many mainstream applications. For example NASTRAN(TradeMark) has its solution sequence 200 for Design Optimization, and MATLAB(TradeMark) has an Optimization Tool box. Other packages, such as ZAERO(TradeMark) aeroelastic panel code and the CFL3D(TradeMark) Navier-Stokes solver have no built in optimizer. The goal of the tool development is to generate a central executive capable of using disparate software packages ina cross platform network environment so as to quickly perform optimization and design tasks in a cohesive streamlined manner. A provided figure (Figure 1) shows a typical set of tools and their relation to the central executive. Optimization can take place within each individual too, or in a loop between the executive and the tool, or both.
Multidisciplinary Optimization for Aerospace Using Genetic Optimization
NASA Technical Reports Server (NTRS)
Pak, Chan-gi; Hahn, Edward E.; Herrera, Claudia Y.
2007-01-01
In support of the ARMD guidelines NASA's Dryden Flight Research Center is developing a multidisciplinary design and optimization tool This tool will leverage existing tools and practices, and allow the easy integration and adoption of new state-of-the-art software. Optimization has made its way into many mainstream applications. For example NASTRAN(TradeMark) has its solution sequence 200 for Design Optimization, and MATLAB(TradeMark) has an Optimization Tool box. Other packages, such as ZAERO(TradeMark) aeroelastic panel code and the CFL3D(TradeMark) Navier-Stokes solver have no built in optimizer. The goal of the tool development is to generate a central executive capable of using disparate software packages ina cross platform network environment so as to quickly perform optimization and design tasks in a cohesive streamlined manner. A provided figure (Figure 1) shows a typical set of tools and their relation to the central executive. Optimization can take place within each individual too, or in a loop between the executive and the tool, or both.
PYTRANSIT: fast and easy exoplanet transit modelling in PYTHON
NASA Astrophysics Data System (ADS)
Parviainen, Hannu
2015-07-01
We present a fast and user friendly exoplanet transit light-curve modelling package PYTRANSIT, implementing optimized versions of the Giménez and Mandel & Agol transit models. The package offers an object-oriented PYTHON interface to access the two models implemented natively in FORTRAN with OpenMP parallelization. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PYTRANSIT is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations, as a part of a researcher's programming toolkit for building complex, problem-specific analyses.
Computation of temperature induced phase transitions at high pressure
NASA Astrophysics Data System (ADS)
Belonoshko, Anatoly
2014-03-01
Phase transitions at high pressure and temperature is perhaps one of the most controversial topics in high pressure science. There is a number of theoretical methods developed recently to address this problem. Unfortunately, none of them is fully satisfactory, considering stringent requirements to accuracy of the computed free energies of the involved phases. This, in part, explains the variety of the suggested methods. The experimental data is rather controversial as well, probably because the experiments at extreme conditions are difficult. I will provide overview of the theoretical methods that are applied for the computation and simulation of T-induced phase transitions. Both liquid-solid and solid-solid transitions will be covered. Possible sources of the disagreement between theoretical methods as well as between theory and experiment will be illustrated by examples. Insight from simulations will be used to suggest alternative explanations of experimental data. The optimal, at present, method to compute the transitions will be suggested.
ERIC Educational Resources Information Center
Burke, Catherine G.
1982-01-01
Criticizes eight commonly held notions about the value of mass transit systems in public transportation programs. Alternative approaches for improving the quality and quantity of urban transit systems are discussed. (AM)
Youths Transitioning as Adult Learners
ERIC Educational Resources Information Center
Davis, C. Amelia
2014-01-01
This chapter considers how transitions to adulthood have been historically represented and presents alternative ways of thinking about transitions to adulthood through the context of adult basic education programs.
Psychological Aspects of Transitive Verbs
ERIC Educational Resources Information Center
Polzella, Donald J.; Rohrman, Nicholas L.
1970-01-01
The experiments reported here confirmed the findings of earlier researchers that transitive verbs are more difficult to recall than intransitive ones and furthermore established a close relationship between transitive verbs and nouns. Implications for linguistic theory are discussed. (FB)
ERIC Educational Resources Information Center
Burke, Catherine G.
1982-01-01
Criticizes eight commonly held notions about the value of mass transit systems in public transportation programs. Alternative approaches for improving the quality and quantity of urban transit systems are discussed. (AM)
Transitional Programs: Boom or Bane?
ERIC Educational Resources Information Center
Brewer, Jo Ann
1990-01-01
Discusses the maturationist, behaviorist, and cognitive interactionist views of transitional programs. Research on transitional programs and possible effects of such programs on kindergarten and first grade classes is discussed. (BG)
NASA Astrophysics Data System (ADS)
Åström, J. A.; Latva-Kokko, M.; Timonen, J.
2003-01-01
An inflated closed loop (or membrane) is used to demonstrate a dynamic rigidity transition that occurs when impact energy is added to the loop in static equilibrium at zero temperature. The only relevant parameter in this transition is the ratio of the energy needed to collapse the loop and the impact energy. When this ratio is below a threshold value close to unity, the loop collapses into a high-entropy floppy state, and it does not return to the rigid state unless the impact energy can escape. The internal oscillations are in the floppy state dominated by 1/f2 noise. When the ratio is above the threshold, the loop does not collapse, and the internal oscillations resulting from the impact are dominated by the eigenfrequencies of the stretched membrane. In this state, the loop can bounce for a long time. It is still an open question whether bouncing will eventually vanish or whether a stationary bouncing state will be reached. The dynamic transition between the floppy and the rigid state is discontinuous.
NASA Technical Reports Server (NTRS)
Reynolds, R.; White, C.
1986-01-01
A computer model capable of analyzing the flow field in the transition liner of small gas turbine engines is developed. A FORTRAN code has been assembled from existing codes and physical submodels and used to predict the flow in several test geometries which contain characteristics similar to transition liners, and for which experimental data was available. Comparisons between the predictions and measurements indicate that the code produces qualitative results but that the turbulence models, both K-E and algebraic Reynolds Stress, underestimate the cross-stream diffusion. The code has also been used to perform a numerical experiment to examine the effect of a variety of parameters on the mixing process in transition liners. Comparisons illustrate that geometries with significant curvature show a drift of the jet trajectory toward the convex wall and weaker wake region vortices and decreased penetration for jets located on the convex wall of the liner, when compared to jets located on concave walls. Also shown were the approximate equivalency of angled slots and round holes and a technique by which jet mixing correlations developed for rectangular channels can be used for can geometries.
NASA Technical Reports Server (NTRS)
1992-01-01
NASA science publications have used the metric system of measurement since 1970. Although NASA has maintained a metric use policy since 1979, practical constraints have restricted actual use of metric units. In 1988, an amendment to the Metric Conversion Act of 1975 required the Federal Government to adopt the metric system except where impractical. In response to Public Law 100-418 and Executive Order 12770, NASA revised its metric use policy and developed this Metric Transition Plan. NASA's goal is to use the metric system for program development and functional support activities to the greatest practical extent by the end of 1995. The introduction of the metric system into new flight programs will determine the pace of the metric transition. Transition of institutional capabilities and support functions will be phased to enable use of the metric system in flight program development and operations. Externally oriented elements of this plan will introduce and actively support use of the metric system in education, public information, and small business programs. The plan also establishes a procedure for evaluating and approving waivers and exceptions to the required use of the metric system for new programs. Coordination with other Federal agencies and departments (through the Interagency Council on Metric Policy) and industry (directly and through professional societies and interest groups) will identify sources of external support and minimize duplication of effort.
NASA Astrophysics Data System (ADS)
NASA science publications have used the metric system of measurement since 1970. Although NASA has maintained a metric use policy since 1979, practical constraints have restricted actual use of metric units. In 1988, an amendment to the Metric Conversion Act of 1975 required the Federal Government to adopt the metric system except where impractical. In response to Public Law 100-418 and Executive Order 12770, NASA revised its metric use policy and developed this Metric Transition Plan. NASA's goal is to use the metric system for program development and functional support activities to the greatest practical extent by the end of 1995. The introduction of the metric system into new flight programs will determine the pace of the metric transition. Transition of institutional capabilities and support functions will be phased to enable use of the metric system in flight program development and operations. Externally oriented elements of this plan will introduce and actively support use of the metric system in education, public information, and small business programs. The plan also establishes a procedure for evaluating and approving waivers and exceptions to the required use of the metric system for new programs. Coordination with other Federal agencies and departments (through the Interagency Council on Metric Policy) and industry (directly and through professional societies and interest groups) will identify sources of external support and minimize duplication of effort.
2015-08-31
Saturn's moon Dione crosses the face of the giant planet in this view, a phenomenon astronomers call a transit. Transits play an important role in astronomy and can be used to study the orbits of planets and their atmospheres, both in our solar system and in others. By carefully timing and observing transits in the Saturn system, like that of Dione (698 miles or 1123 kilometers across), scientists can more precisely determine the orbital parameters of Saturn's moons. This view looks toward the unilluminated side of the rings from about 0.3 degrees below the ring plane. The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on May 21, 2015. The view was acquired at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 119 degrees. Image scale is 9 miles (14 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18330
Column continuous transition functions
NASA Astrophysics Data System (ADS)
Li, Yangrong
2007-04-01
A column continuous transition function is by definition a standard transition function P(t) whose every column is continuous for t[greater-or-equal, slanted]0 in the norm topology of bounded sequence space l[infinity]. We will prove that it has a stable q-matrix and that there exists a one-to-one relationship between column continuous transition functions and increasing integrated semigroups on l[infinity]. Using the theory of integrated semigroups, we give some necessary and sufficient conditions under which the minimal q-function is column continuous, in terms of its generator (of the Markov semigroup) as well as its q-matrix. Furthermore, we will construct all column continuous Q-functions for a conservative, single-exit and column bounded q-matrix Q. As applications, we find that many interesting continuous-time Markov chains (CTMCs), say Feller-Reuter-Riley processes, monotone processes, birth-death processes and branching processes, etc., have column continuity.
The transition to agricultural sustainability
Ruttan, Vernon W.
1999-01-01
The transition to sustainable growth in agricultural production during the 21st century will take place within the context of a transition to a stable population and a possible transition to a stable level of material consumption. If the world fails to successfully navigate a transition to sustainable growth in agricultural production, the failure will be due more to a failure in the area of institutional innovation than to resource and environmental constraints. PMID:10339524
Visual Analytics Technology Transition Progress
Scholtz, Jean; Cook, Kristin A.; Whiting, Mark A.; Lemon, Douglas K.; Greenblatt, Howard
2009-09-23
The authors provide a description of the transition process for visual analytic tools and contrast this with the transition process for more traditional software tools. This paper takes this into account and describes a user-oriented approach to technology transition including a discussion of key factors that should be considered and adapted to each situation. The progress made in transitioning visual analytic tools in the past five years is described and the challenges that remain are enumerated.
Analyses of some exoplanets' transits and transit timing variations
NASA Astrophysics Data System (ADS)
Püsküllü, ćaǧlar; Soydugan, Faruk
2017-02-01
We present solutions of the transit light curves and transit timing variations (TTVs) analyses of the exoplanets HAT-P-5b, HAT-P-9b and HAT-P-25b. Transit light curves were collected at Çanakkale Onsekiz Mart University Observatory and TUBITAK National Observatory. The models were produced by WINFITTER program and stellar, planetary and orbital properties were obtained and discussed. We gave new transit times and generated TTVs with them by appending additional data based on Exoplanet Transit Database (ETD). Significant signals at the TTVs were also investigated.
The Community Vocational Transition Center.
ERIC Educational Resources Information Center
Botterbusch, Karl F.; Smith, Christopher A.
This monograph outlines a model procedure for developing and running a community vocational transition center that would assist workers in making various planned and unplanned vocational transitions throughout their lives by offering a comprehensive array of vocational assessment and transition services. The first chapter addresses the question of…
Reconstructing Transition Knowledge in Taiwan
ERIC Educational Resources Information Center
Cheng, Chen-chen
2012-01-01
Taking a post-colonial stand and using school to work transition as an example, the author re-examines the special education discourses in Taiwan and attempts to construct alternate understandings of transition from sociological and cultural perspectives. A review of past transition literature and a survey of the educational background of the…
Wald, Arnold
2002-08-01
The diagnosis of slow transit functional constipation is based upon diagnostic testing of patients with idiopathic constipation who responded poorly to conservative measures such as fiber supplements, fluids, and stimulant laxatives. These tests include barium enema or colonoscopy, colonic transit of radio-opaque markers, anorectal manometry, and expulsion of a water-filled balloon. Plain abdominal films can identify megacolon, which can be further characterized by barium or gastrografin studies. Colonic transit of radio-opaque markers identifies patients with slow transit with stasis of markers in the proximal colon. However, anorectal function should be characterized to exclude outlet dysfunction, which may coexist with colonic inertia. Because slow colonic transit is defined by studies during which patients consume a high-fiber diet, fiber supplements are generally not effective, nor are osmotic laxatives that consist of unabsorbed sugars. Stimulant laxatives are considered first-line therapy, although studies often show a diminished colonic motor response to such agents. There is no evidence to suggest that chronic use of such laxatives is harmful if they are used two to three times per week. Polyethylene glycol with or without electrolytes may be useful in a minority of patients, often combined with misoprostol. I prefer to start with misoprostol 200 mg every other morning and increase to tolerance or efficacy. I see no advantage in prescribing misoprostol on a TID or QID basis or even daily because it increases cramping unnecessarily. This drug is not acceptable in young women who wish to become pregnant. An alternative may be colchicine, which is reported to be effective when given as 0.6 mg TID. Long-term efficacy has not been studied. Finally, biofeedback is a risk-free approach that has been reported as effective in approximately 60% of patients with slow transit constipation in the absence of outlet dysfunction. Although difficult to understand
Lokutsievskiy, Lev V
2011-05-31
This paper is concerned with the optimal search of an object at rest with unknown exact position in the n-dimensional space. A necessary condition for optimality of a trajectory is obtained. An explicit form of a differential equation for an optimal trajectory is found while searching over R-strongly convex sets. An existence theorem is also established. Bibliography: 8 titles.
Components of Comprehensive and Effective Transitional Care.
Naylor, Mary D; Shaid, Elizabeth C; Carpenter, Deborah; Gass, Brianna; Levine, Carol; Li, Jing; Malley, Ann; McCauley, Kathleen; Nguyen, Huong Q; Watson, Heather; Brock, Jane; Mittman, Brian; Jack, Brian; Mitchell, Suzanne; Callicoatte, Becky; Schall, John; Williams, Mark V
2017-04-03
Transitional care (TC) has received widespread attention from researchers, health system leaders, clinicians, and policy makers as they attempt to improve health outcomes and reduce preventable hospital readmissions, yet little is known about the critical elements of effective TC and how they relate to patients' and caregivers' needs and experiences. To address this gap, the Patient-Centered Outcomes Research Institute (PCORI) funded a national study, Achieving patient-centered Care and optimized Health In care transitions by Evaluating the Value of Evidence (Project ACHIEVE). A primary aim of the study is the identification of TC components that yield desired patient and caregiver outcomes. Project ACHIEVE established a multistakeholder workgroup to recommend essential TC components for vulnerable Medicare beneficiaries. Guided by a review of published evidence, the workgroup identified and defined a preliminary set of components and then analyzed how well the set aligned with real-world patients' and caregivers' experiences. Through this process, the workgroup identified eight TC components: patient engagement, caregiver engagement, complexity and medication management, patient education, caregiver education, patients' and caregivers' well-being, care continuity, and accountability. Although the degree of attention given to each component will vary based on the specific needs of patients and caregivers, workgroup members agree that health systems need to address all components to ensure optimal TC for all Medicare beneficiaries.
Optimally controlling the human connectome: the role of network topology
Betzel, Richard F.; Gu, Shi; Medaglia, John D.; Pasqualetti, Fabio; Bassett, Danielle S.
2016-01-01
To meet ongoing cognitive demands, the human brain must seamlessly transition from one brain state to another, in the process drawing on different cognitive systems. How does the brain’s network of anatomical connections help facilitate such transitions? Which features of this network contribute to making one transition easy and another transition difficult? Here, we address these questions using network control theory. We calculate the optimal input signals to drive the brain to and from states dominated by different cognitive systems. The input signals allow us to assess the contributions made by different brain regions. We show that such contributions, which we measure as energy, are correlated with regions’ weighted degrees. We also show that the network communicability, a measure of direct and indirect connectedness between brain regions, predicts the extent to which brain regions compensate when input to another region is suppressed. Finally, we identify optimal states in which the brain should start (and finish) in order to minimize transition energy. We show that the optimal target states display high activity in hub regions, implicating the brain’s rich club. Furthermore, when rich club organization is destroyed, the energy cost associated with state transitions increases significantly, demonstrating that it is the richness of brain regions that makes them ideal targets. PMID:27468904
Fluctuations and Redundancy in Optimal Transport Networks
NASA Astrophysics Data System (ADS)
Corson, Francis
2010-01-01
The structure of networks that provide optimal transport properties has been investigated in a variety of contexts. While many different formulations of this problem have been considered, it is recurrently found that optimal networks are trees. It is shown here that this result is contingent on the assumption of a stationary flow through the network. When time variations or fluctuations are allowed for, a different class of optimal structures is found, which share the hierarchical organization of trees yet contain loops. The transitions between different network topologies as the parameters of the problem vary are examined. These results may have strong implications for the structure and formation of natural networks, as is illustrated by the example of leaf venation networks.
Aircraft configuration optimization including optimized flight profiles
NASA Technical Reports Server (NTRS)
Mccullers, L. A.
1984-01-01
The Flight Optimization System (FLOPS) is an aircraft configuration optimization program developed for use in conceptual design of new aircraft and in the assessment of the impact of advanced technology. The modular makeup of the program is illustrated. It contains modules for preliminary weights estimation, preliminary aerodynamics, detailed mission performance, takeoff and landing, and execution control. An optimization module is used to drive the overall design and in defining optimized profiles in the mission performance. Propulsion data, usually received from engine manufacturers, are used in both the mission performance and the takeoff and landing analyses. Although executed as a single in-core program, the modules are stored separately so that the user may select the appropriate modules (e.g., fighter weights versus transport weights) or leave out modules that are not needed.
Chandler, K.; Eudy, L.
2007-03-01
This report provides an evaluation of three prototype fuel cell-powered transit buses operating at AC Transit in Oakland, California, and six baseline diesel buses similar in design to the fuel cell buses.
Optimal aircraft performance during microburst encounter
NASA Technical Reports Server (NTRS)
Psiaki, Mark L.; Stengel, Robert F.
1991-01-01
The effects of microburst characteristics on the optimal penetration performance of jet transport and general aviation aircraft are presented. The purpose is to determine the best possible performance that can be achieved in a broad range of microbursts. A secondary goal is to illustrate good strategies for dealing with a range of microbursts during takeoff and landing. Over 1100 optimal trajectories were computed for two aircraft types flying through idealized microbursts using a Successive Quadratic Programs trajectory optimization algorithm. Contours of safety metrics are plotted as functions of the length scales, magnitudes, and locations of horizontal wind shears and vertical downdrafts. These performance contours show three length-scale regimes for optimal microburst penetration. At short length scales, hazards usually associated with gustiness predominate (e.g., high normal load factor, rotational upset). At intermediate length scales, a degraded ability to maintain flight path and/or vertical velocity poses the most serious threat. At very long microburst length scales, excessive touchdown velocities may result. The ability to transit a microburst successfully also varies strongly with microburst location. The results show that both aircraft types could penetrate some very severe microbursts if optimal control histories were followed. Nevertheless, these control strategies assume perfect prior knowledge of the wind, and practical limits to successful encounter with real-time control capabilities would be lower. The optimally controlled jet transport can successfully penetrate higher intensity microbursts than can the general aviation aircraft.
Computational process optimization of array edges
NASA Astrophysics Data System (ADS)
Küchler, Bernd; Shamsuarov, Artem; Mülders, Thomas; Klostermann, Ulrich; Yang, Seung-Hune; Moon, Seongho; Domnenko, Vitaliy; Park, Sung-Woon
2012-03-01
DRAM chip space is mainly determined by the size of the memory cell array patterns which consist of periodic memory cell features. Resolution Enhancement Techniques are used to optimize the periodic pattern process performance. This is often realized with aggressively coherent illumination sources supporting the periodic pattern pitch only and making an array edge correction very difficult. The edge can be the most critical pattern since it forms the transition from periodic patterns to non periodic periphery, so it combines the most critical pitch and highest susceptibility to defocus. Non functional dummy structures are very effective to support the outermost edge but are very expensive, so their reduction or avoidance directly increases chip space efficiency. This paper focuses on how to optimize the DRAM array edge automatically in contrast to manual optimization approaches that were used effectively but at high cost. We will show how to squeeze out the masks degrees of freedom to stay within tight pattern tolerances. In that way we minimize process variations and the need of costly non-functional dummy structures. To obtain the best possible results the optimization has to account for complex boundary conditions: correct resist effect prediction, mask manufacturability constraints, low dose, low MEEF, conservation of symmetries and SRAF printing, simultaneous optimization of main features and SRAFs. By incorporating these complex boundary conditions during optimization we aim to provide first time right layouts without the need for any post processing.
Structural transitions in nanoscale systems
NASA Astrophysics Data System (ADS)
Yoon, Mina
In this work I investigate three different materials: nanoscale carbon systems, ferrofluid systems, and molecular-electronic devices. In particular, my study is focused on the theoretical understanding of structural changes and the associated electronic, mechanical, and magnetic properties of these materials. To study the equilibrium packing of fullerenes in carbon nanotube peapods optimization techniques were applied. In agreement with experimental measurements, my results for nanotubes containing fullerenes with 60--84 atoms indicate that the axial separation between the fullerenes is smaller than in the bulk crystal. The reduction of the inter-fullerene distance and also the structural relaxation of fullerenes result from a large internal pressure within the peapods. This naturally induced "static" pressure may qualify nanotubes as nanoscale autoclaves for chemical reactions. Combining total energy calculations with a search of phase space, I investigated the microscopic fusion mechanism of C60 fullerenes. I show that the (2+2) cycloaddition reaction, a necessary precursor for fullerene fusion, can be accelerated inside a nanotube. Fusion occurs along the minimum energy path as a finite sequence of Stone-Wales (SW) transformations. A detailed analysis of the transition states shows that Stone-Wales transformations are multi-step processes. I propose a new microscopic mechanism to explain the unusually fast fusion process of carbon nanotubes. The detailed pathway for two adjacent (5, 5) nanotubes to gradually merge into a (10, 10) tube, and the transition states have been identified. The propagation of the fused region is energetically favorable and proceeds in a morphology reminiscent of a Y-junction via a so called zipper mechanism, involving only SW bond rearrangements with low activation barriers. Using density functional theory, the equilibrium structure, stability, and electronic properties of nanostructured, hydrogen terminated diamond fragments have been
Interactive visualization and analysis of transitional flow.
Johnson, Gregory P; Calo, Victor M; Gaither, Kelly P
2008-01-01
A stand-alone visualization application has been developed by a multi-disciplinary, collaborative team with the sole purpose of creating an interactive exploration environment allowing turbulent flow researchers to experiment and validate hypotheses using visualization. This system has specific optimizations made in data management, caching computations, and visualization allowing for the interactive exploration of datasets on the order of 1TB in size. Using this application, the user (co-author Calo) is able to interactively visualize and analyze all regions of a transitional flow volume, including the laminar, transitional and fully turbulent regions. The underlying goal of the visualizations produced from these transitional flow simulations is to localize turbulent spots in the laminar region of the boundary layer, determine under which conditions they form, and follow their evolution. The initiation of turbulent spots, which ultimately lead to full turbulence, was located via a proposed feature detection condition and verified by experimental results. The conditions under which these turbulent spots form and coalesce are validated and presented.
Solar diameter with 2012 Venus Transit
NASA Astrophysics Data System (ADS)
Sigismondi, C.
2012-06-01
The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement of the solar diameter with the Venus transit of 5/6 June 2012 with an unprecedented accuracy, and with absolute calibration given by the ephemerides.
Measuring Solar Diameter with 2012 Venus Transits
NASA Astrophysics Data System (ADS)
Sigismondi, Costantino
The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement of the solar diameter with the Venus transit of 5/6 June 2012 with an unprecedented accuracy, and with absolute calibration given by the ephemerides.
Salinas, Daniel; Baker, David P
2015-01-01
Objective Previous studies found that developed and developing countries present opposite education-overweight gradients but have not considered the dynamics at different levels of national development. A U-inverted curve is hypothesized to best describe the education-overweight association. It is also hypothesized that as the nutrition transition unfolds within nations the shape of education-overweight curve change. Design Multi-level logistic regression estimates the moderating effect of the nutrition transition at the population level on education-overweight gradient. At the individual level, a non-linear estimate of the education association assesses the optimal functional form of the association across the nutrition transition. Setting Twenty-two administrations of the Demographic and Health Survey, collected at different time points across the nutrition transition in nine Latin American/Caribbean countries. Subjects Mothers of reproductive age (15–49) in each administration (n 143,258). Results In the pooled sample, a non-linear education gradient on mothers‘ overweight is found; each additional year of schooling increases the probability of being overweight up to the end of primary schooling, after which each additional year of schooling decreases the probability of overweight. Also, as access to diets of high animal fats and sweeteners increases over time, the curve‘s critical point moves to lower education levels, the detrimental positive effect of education diminishes, and both occur as the overall risk of overweight increases with greater access to harmful diets. Conclusions Both hypotheses are supported. As the nutrition transition progresses, the education-overweight curve steadily shifts to a negative linear association with higher average risk of overweight; and education, at increasingly lower levels, acts as a “social vaccine” against increasing risk of overweight. These empirical patterns fit the general “population education
Condensation phase transitions in ferrofluids.
Iskakova, L Yu; Smelchakova, G A; Zubarev, A Yu
2009-01-01
Experiments show that under suitable conditions magnetic particles in ferrofluids and other polar suspensions undergo condensation phase transitions and form dense liquidlike or solidlike phases. The problem of fundamental features and scenarios of the phase transitions is one of the central problems of the physics of these systems. This work deals with the theoretical study of scenarios of condensation phase transitions in ferrofluids, consisting of identical magnetic particles. Our results show that, unlike the classical condensation phase transitions, the appearance of the linear chains precedes the magnetic particle bulk condensation. The effect of the chains on the diagrams of the equilibrium phase transitions is studied.
McGuire-Snieckus, Rebecca
2014-01-01
Optimism is generally accepted by psychiatrists, psychologists and other caring professionals as a feature of mental health. Interventions typically rely on cognitive-behavioural tools to encourage individuals to ‘stop negative thought cycles’ and to ‘challenge unhelpful thoughts’. However, evidence suggests that most individuals have persistent biases of optimism and that excessive optimism is not conducive to mental health. How helpful is it to facilitate optimism in individuals who are likely to exhibit biases of optimism already? By locating the cause of distress at the individual level and ‘unhelpful’ cognitions, does this minimise wider systemic social and economic influences on mental health? PMID:25237497
Mikhalevich, V.S.; Sergienko, I.V.; Zadiraka, V.K.; Babich, M.D.
1994-11-01
This article examines some topics of optimization of computations, which have been discussed at 25 seminar-schools and symposia organized by the V.M. Glushkov Institute of Cybernetics of the Ukrainian Academy of Sciences since 1969. We describe the main directions in the development of computational mathematics and present some of our own results that reflect a certain design conception of speed-optimal and accuracy-optimal (or nearly optimal) algorithms for various classes of problems, as well as a certain approach to optimization of computer computations.
NASA Technical Reports Server (NTRS)
Herbert, Thorwald
1998-01-01
We have further developed our capabilities to analyze transition in turbine boundary layers from first principles by integrating the nonlinear parabolized stability equations (PSE) with improved initial and boundary conditions. With modified iteration schemes, we are able to proceed deeper into the transition region where skin friction coefficient and heat transfer coefficient significantly increase. Initial and boundary conditions at elevated turbulence levels can be derived by receptivity analysis. Test runs for ERCOFTAC test case T3A at 2.4\\% turbulence level provide results in good agreement with the experimental data. The sharper minimum of the skin coefficient also shown by DNS results is likely due to the missing intermittency. The method has been applied to various experimentally studied turbine blades (UTRC, VKI, Zierke, Langston, Hippensteele, and others). The PSE results, though physically reasonable, do not agree as well as expected with the experimental findings. We have, therefore, performed an extensive search for the reasons of the seemingly systematic deviations. A first source of uncertainty has been found in the often insufficient documentation of the experiments (e.g. on blockage by end-wall boundary layers). However, variation of the relevant parameters does not lead to more satisfactory agreement. A second reason has been found in the "standard procedure" which considers a 2D flow at midspan and uses a panel code and subsequent boundary-layer code to obtain the laminar basic flow for the transition analysis. Comparison with the pressure distribution obtained with a 3D design code (RVC3D) shows significant three-dimensionality of the flow (e.g. in the UTRC experiments). The spanwise variation has been neglected in our original PSE code. To overcome this problem, we have developed the PSE/3D for fully 3D boundary layers to account for streamwise and spanwise variations. Since the design code does not provide the boundary-layer flow with
Integrated controls design optimization
Lou, Xinsheng; Neuschaefer, Carl H.
2015-09-01
A control system (207) for optimizing a chemical looping process of a power plant includes an optimizer (420), an income algorithm (230) and a cost algorithm (225) and a chemical looping process models. The process models are used to predict the process outputs from process input variables. Some of the process in puts and output variables are related to the income of the plant; and some others are related to the cost of the plant operations. The income algorithm (230) provides an income input to the optimizer (420) based on a plurality of input parameters (215) of the power plant. The cost algorithm (225) provides a cost input to the optimizer (420) based on a plurality of output parameters (220) of the power plant. The optimizer (420) determines an optimized operating parameter solution based on at least one of the income input and the cost input, and supplies the optimized operating parameter solution to the power plant.
NASA Technical Reports Server (NTRS)
Venter, Gerhard; Sobieszczanski-Sobieski Jaroslaw
2002-01-01
The purpose of this paper is to show how the search algorithm known as particle swarm optimization performs. Here, particle swarm optimization is applied to structural design problems, but the method has a much wider range of possible applications. The paper's new contributions are improvements to the particle swarm optimization algorithm and conclusions and recommendations as to the utility of the algorithm, Results of numerical experiments for both continuous and discrete applications are presented in the paper. The results indicate that the particle swarm optimization algorithm does locate the constrained minimum design in continuous applications with very good precision, albeit at a much higher computational cost than that of a typical gradient based optimizer. However, the true potential of particle swarm optimization is primarily in applications with discrete and/or discontinuous functions and variables. Additionally, particle swarm optimization has the potential of efficient computation with very large numbers of concurrently operating processors.
Optimal driving of Bose-Einstein condensates in optical cavities
Caneva, T.; Calarco, T.; Montangero, S.
2014-12-04
We apply quantum optimal control to enhance the performance of the experimental setup of Ref. [1], speeding up the system dynamics at time scales of the order of the quantum speed limit. We perform a fast crossing of the quantum phase transition the system undergoes under realistic experimental conditions, and we present a new scaling-based strategy to compute optimal pulses for systems at the thermodynamical limit.
Heuristic optimization of the scanning path of particle therapy beams.
Pardo, J; Donetti, M; Bourhaleb, F; Ansarinejad, A; Attili, A; Cirio, R; Garella, M A; Giordanengo, S; Givehchi, N; La Rosa, A; Marchetto, F; Monaco, V; Pecka, A; Peroni, C; Russo, G; Sacchi, R
2009-06-01
Quasidiscrete scanning is a delivery strategy for proton and ion beam therapy in which the beam is turned off when a slice is finished and a new energy must be set but not during the scanning between consecutive spots. Different scanning paths lead to different dose distributions due to the contribution of the unintended transit dose between spots. In this work an algorithm to optimize the scanning path for quasidiscrete scanned beams is presented. The classical simulated annealing algorithm is used. It is a heuristic algorithm frequently used in combinatorial optimization problems, which allows us to obtain nearly optimal solutions in acceptable running times. A study focused on the best choice of operational parameters on which the algorithm performance depends is presented. The convergence properties of the algorithm have been further improved by using the next-neighbor algorithm to generate the starting paths. Scanning paths for two clinical treatments have been optimized. The optimized paths are found to be shorter than the back-and-forth, top-to-bottom (zigzag) paths generally provided by the treatment planning systems. The gamma method has been applied to quantify the improvement achieved on the dose distribution. Results show a reduction of the transit dose when the optimized paths are used. The benefit is clear especially when the fluence per spot is low, as in the case of repainting. The minimization of the transit dose can potentially allow the use of higher beam intensities, thus decreasing the treatment time. The algorithm implemented for this work can optimize efficiently the scanning path of quasidiscrete scanned particle beams. Optimized scanning paths decrease the transit dose and lead to better dose distributions.
A translational evaluation of transitions.
Jessel, Joshua; Hanley, Gregory P; Ghaemmaghami, Mahshid
2016-06-01
Transitions with nonhuman animals are typically framed as inescapable changes in signaled reinforcement schedules that result in a pause in responding unique to switches from rich to lean schedules. Pausing is considered to be a function of the aversive qualities of the contrasting reinforcement schedules. Transitions are typically framed in applied research as physical changes in location that evoke problem behavior maintained by the escape of an aversive event or resumption of a preferred event. We attempted to extend the basic framing of transitions to behaviors and contexts of social significance and evaluate a novel treatment for the problem of dawdling by 3 boys who had been diagnosed with autism spectrum disorder during rich-to-lean transitions. Dawdling during physical transitions was most readily observed when transitioning to lean contexts in Experiment 1. We then shortened transition duration in Experiment 2 by programming unsignaled and probabilistic rich reinforcement in the upcoming context.
Pivotal Transitions - Historical and Today
NASA Astrophysics Data System (ADS)
Hurley, M.
2008-08-01
The goal of this paper is to enable readers to better "design" successful transitions that move Science and Technology or Research and Development (S&T/R&D) technologies and systems into operational capabilities for users. Transitions from S&T/R&D into acquisition and operations are challenging and critical to providing capab ilities to end users. Two historical examples, the Global Positioning System (GPS) and the Disaster Monitoring Constellation (DMC), are explored. Two current examples are also explored, including one from Operationally Responsive Space (ORS) which is in th e early stages of transition. While transitions are necessary, transition periods are inherently challenging and dynamically changing situations. These situations must be carefully managed and led in order to succeed. Characteristics, approaches, and incentives that foster effective transitions are discussed. Understanding the transition process and the communities involved allows one to maximize the chance of successfully moving an S&T/R&D development into an operational capability supporting end users.
Ornithopter transition trajectories
NASA Astrophysics Data System (ADS)
Dietl, John M.; Garcia, Ephrahim
2010-04-01
The design of stable trim conditions for forward flight and for hover has been achieved. In forward flight, an ornithopter is configured like a conventional airplane or large bird. Its fuselage is essentially horizontal and the wings heave in a vertical plane. In hover, however, the body pitches vertically so that the wing stroke in the horizontal plane. Thrust directed downward, the vehicle remains aloft while the downdraft envelops the tail to provide enough flow for vehicle control and stabilization. To connect these trajectories dynamically is the goal. The naïve approach-to choose two stable trajectories and switch between them-has been accomplished. A new approach is to establish an open-loop trajectory through a trajectory optimization algorithm-optimized for shortest altitude drop, shortest stopping distance, or lowest energy consumption.
MINEHOUND: transition to production
NASA Astrophysics Data System (ADS)
Daniels, David J.; Curtis, Paul; Hunt, Nigel; Braunstein, Jürgen; Merz, Armin
2007-04-01
The UK Department for International Development (DfID), in collaboration with the German Foreign Ministry (Auswärtiges Amt), contracted ERA Technology to carry out extensive field trials in Cambodia, Bosnia and Angola of an advanced technology, dual sensor, and hand-held landmine detector system called MINEHOUND TM. This detector combines a metal detector with a Ground Penetrating Radar (GPR). As a result of extremely successful trials MINEHOUND TM was developed as a product by ERA Technology and Vallon GmbH and has been available for sale since late 2006. This paper describes the transition to production of the detector.
Transition Metal Switchable Mirror
2009-01-01
The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm
Transition Metal Switchable Mirror
2009-08-21
The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.
Transition Metal Switchable Mirror
None
2016-07-12
The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.
Transition Metal Switchable Mirror
None
2016-07-12
The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm
NASA Astrophysics Data System (ADS)
vanden-Eijnden, E.
The dynamical behavior of many systems arising in physics, chemistry, biology, etc. is dominated by rare but important transition events between long lived states. For over 70 years, transition state theory (TST) has provided the main theoretical framework for the description of these events [17,33,34]. Yet, while TST and evolutions thereof based on the reactive flux formalism [1, 5] (see also [30,31]) give an accurate estimate of the transition rate of a reaction, at least in principle, the theory tells very little in terms of the mechanism of this reaction. Recent advances, such as transition path sampling (TPS) of Bolhuis, Chandler, Dellago, and Geissler [3, 7] or the action method of Elber [15, 16], may seem to go beyond TST in that respect: these techniques allow indeed to sample the ensemble of reactive trajectories, i.e. the trajectories by which the reaction occurs. And yet, the reactive trajectories may again be rather uninformative about the mechanism of the reaction. This may sound paradoxical at first: what more than actual reactive trajectories could one need to understand a reaction? The problem, however, is that the reactive trajectories by themselves give only a very indirect information about the statistical properties of these trajectories. This is similar to why statistical mechanics is not simply a footnote in books about classical mechanics. What is the probability density that a trajectory be at a given location in state-space conditional on it being reactive? What is the probability current of these reactive trajectories? What is their rate of appearance? These are the questions of interest and they are not easy to answer directly from the ensemble of reactive trajectories. The right framework to tackle these questions also goes beyond standard equilibrium statistical mechanics because of the nontrivial bias that the very definition of the reactive trajectories imply - they must be involved in a reaction. The aim of this chapter is to
Approximating random quantum optimization problems
NASA Astrophysics Data System (ADS)
Hsu, B.; Laumann, C. R.; Läuchli, A. M.; Moessner, R.; Sondhi, S. L.
2013-06-01
We report a cluster of results regarding the difficulty of finding approximate ground states to typical instances of the quantum satisfiability problem k-body quantum satisfiability (k-QSAT) on large random graphs. As an approximation strategy, we optimize the solution space over “classical” product states, which in turn introduces a novel autonomous classical optimization problem, PSAT, over a space of continuous degrees of freedom rather than discrete bits. Our central results are (i) the derivation of a set of bounds and approximations in various limits of the problem, several of which we believe may be amenable to a rigorous treatment; (ii) a demonstration that an approximation based on a greedy algorithm borrowed from the study of frustrated magnetism performs well over a wide range in parameter space, and its performance reflects the structure of the solution space of random k-QSAT. Simulated annealing exhibits metastability in similar “hard” regions of parameter space; and (iii) a generalization of belief propagation algorithms introduced for classical problems to the case of continuous spins. This yields both approximate solutions, as well as insights into the free energy “landscape” of the approximation problem, including a so-called dynamical transition near the satisfiability threshold. Taken together, these results allow us to elucidate the phase diagram of random k-QSAT in a two-dimensional energy-density-clause-density space.
Graves, C.E.
1994-08-31
The preparation for decontamination and decommissioning (transition) of the 309 Building is projected to be completed by the end of the fiscal year (FY) 1998. The major stabilization and decontamination efforts include the Plutonium Recycle Test Reactor (PRTR), fuel storage and transfer pits, Transfer Waste (TW) tanks and the Ion Exchange Vaults. In addition to stabilizing contaminated areas, equipment, components, records, waste products, etc., will be dispositioned. All nonessential systems, i.e., heating, ventilation, and air conditioning (HVAC), electrical, monitoring, fluids, etc., will be shut down and drained/de-energized. This will allow securing of the process, laboratory, and office areas of the facility. After that, the facility will be operated at a level commensurate with its surveillance needs while awaiting D&D. The implementation costs for FY 1995 through FY 1998 for the transition activities are estimated to be $1,070K, $2,115K, $2,939K, and $4,762K, respectively. Costs include an assumed company overhead of 20% and a 30% out year contingency.
Planet Demographics from Transits
NASA Astrophysics Data System (ADS)
Howard, Andrew
2015-08-01
From the demographics of planets detected by the Kepler mission, we have learned that there exists approximately one planet per star for planets larger than Earth orbiting inside of 1 AU. We have also learned the relative occurrence of these planets as a function of their orbital periods, sizes, and host star masses and metallicities. In this talk I will review the key statistical findings that the planet size distribution peaks in the range 1-3 times Earth-size, the orbital period distribution is characterized by a power-law cut off at short periods, small planets are more prevalent around small stars, and that approximately 20% of Sun-like stars hosts a planet 1-2 times Earth-size in a habitable zone. Looking forward, I will describe analysis of photometry from the K2 mission that is yielding initial planet discoveries and offering the opportunity to measure planet occurrence in widely separated regions of the galaxy. Finally, I will also discuss recent techniques to discover transiting planets in space-based photometry and to infer planet population properties from the ensemble of detected and non-detected transit signals.
Bluestein, P
1995-12-01
The study of physicians as managed care executives has been relatively recent. Much of what was written in the past focused primarily on doctors who had taken hospital-based administrative positions, especially as medical directors or vice presidents of medical affairs.1 But the '80s brought rising health care costs and the emergence of the "O's"--HMOs, PPOs, UROs, EPOs, PHOs, H2Os, and Uh-Ohs--in response. It also brought a growing number of physicians who traded their white coats and their particular "ologies" for the blue suits of executive management. I am convinced that it is important now, and will be increasingly important in the future, to better understand that transition. That belief led me to undertake, with the help and support of ACPE, the survey that is reported in this article. A questionnaire was sent in 1994 to a random sample of 300 managed care physician executive members of ACPE. Responses were returned by 225 members, a response rate of better than 80 percent. Twenty-five of the responses were not applicable, having been returned by physicians who had never made a transition from clinical careers. The remaining 230 responses form the basis for this report.
1996-10-23
During orbits 423 through 424 on 22 September 1990, NASA's Magellan imaged this impact crater that is located at latitude 10.7 degrees north and longitude 340.7 degrees east. This crater is shown as a representative of Venusian craters that are of the proper diameter (about 15 kilometers) to be 'transitional' in their morphology between 'complex' and irregular' craters. Complex craters account for about 96 percent of all craters on Venus with diameters larger than about 15 kilometers; they are thought to have been formed by the impact of a large, more or less intact, mass of asteroidal material that has not been excessively effected during its passage through the dense Venusian atmosphere. Complex craters are characterized by circular rims, terraced inner wall slopes, well developed ejecta deposits, and flat floors with a central peak or peak ring. Irregular craters make up about 60 percent of the craters with diameters less than about 15 kilometers. Irregular craters are thought to form as the result of the impact of asteroidal projectiles that have been aerodynamically crushed and fragmented during their passage through the atmosphere. Irregular craters are characterized by irregular and/or discontinuous rims and hummocky or multiple floors. The 'transitional' crater shown here has a somewhat circular rim like larger complex craters, but has the hummocky floor and asymmetric ejecta characteristic of smaller irregular craters. http://photojournal.jpl.nasa.gov/catalog/PIA00468
2015-09-13
On Sept. 13, 2015, as NASA's Solar Dynamics Observatory, or SDO, kept up its constant watch on the sun, its view was photobombed not once, but twice. Just as the moon came into SDO's field of view on a path to cross the sun, Earth entered the picture, blocking SDO's view completely. When SDO's orbit finally emerged from behind Earth, the moon was just completing its journey across the sun's face. Though SDO sees dozens of Earth eclipses and several lunar transits each year, this is the first time ever that the two have coincided. SDO's orbit usually gives us unobstructed views of the sun, but Earth's revolution around the sun means that SDO's orbit passes behind Earth twice each year, for two to three weeks at a time. During these phases, Earth blocks SDO's view of the sun for anywhere from a few minutes to over an hour once each day. Earth's outline looks fuzzy, while the moon's is crystal-clear. This is because-while the planet itself completely blocks the sun's light-Earth's atmosphere is an incomplete barrier, blocking different amounts of light at different altitudes. However, the moon has no atmosphere, so during the transit we can see the crisp edges of the moon's horizon. http://photojournal.jpl.nasa.gov/catalog/PIA19949
High pressure phase transition and elastic properties of americium telluride
NASA Astrophysics Data System (ADS)
Aynyas, Mahendra; Rukmangad, Aditi; Arya, B. S.; Sanyal, S. P.
2013-06-01
The structural and elastic properties of Americium Telluride (AmTe) have been investigated by using a modified inter-ionic potential theory (MIPT). This theory is capable of explaining first order phase transition with a crystallographic change NaCl to CsCl structure for this compound. The values of optimized lattice constant, phase transition pressure, zero pressure bulk modulus and second order elastic constants (C11, C44) agree well with their corresponding experimental data. Debye temperature (θD) is also calculated for this compound for the first time.
Supercomputer optimizations for stochastic optimal control applications
NASA Technical Reports Server (NTRS)
Chung, Siu-Leung; Hanson, Floyd B.; Xu, Huihuang
1991-01-01
Supercomputer optimizations for a computational method of solving stochastic, multibody, dynamic programming problems are presented. The computational method is valid for a general class of optimal control problems that are nonlinear, multibody dynamical systems, perturbed by general Markov noise in continuous time, i.e., nonsmooth Gaussian as well as jump Poisson random white noise. Optimization techniques for vector multiprocessors or vectorizing supercomputers include advanced data structures, loop restructuring, loop collapsing, blocking, and compiler directives. These advanced computing techniques and superconducting hardware help alleviate Bellman's curse of dimensionality in dynamic programming computations, by permitting the solution of large multibody problems. Possible applications include lumped flight dynamics models for uncertain environments, such as large scale and background random aerospace fluctuations.
Optimization and optimal statistics in neuroscience
NASA Astrophysics Data System (ADS)
Brookings, Ted
Complex systems have certain common properties, with power law statistics being nearly ubiquitous. Despite this commonality, we show that a variety of mechanisms can be responsible for complexity, illustrated by the example of a lattice on a Cayley Tree. Because of this, analysis must probe more deeply than merely looking for power laws, instead details of the dynamics must be examined. We show how optimality---a frequently-overlooked source of complexity---can produce typical features such as power laws, and describe inherent trade-offs in optimal systems, such as performance vs. robustness to rare disturbances. When applied to biological systems such as the nervous system, optimality is particularly appropriate because so many systems have identifiable purpose. We show that the "grid cells" in rats are extremely efficient in storing position information. Assuming the system to be optimal allows us to describe the number and organization of grid cells. By analyzing systems from an optimal perspective provides insights that permit description of features that would otherwise be difficult to observe. As well, careful analysis of complex systems requires diligent avoidance of assumptions that are unnecessary or unsupported. Attributing unwarranted meaning to ambiguous features, or assuming the existence of a priori constraints may quickly lead to faulty results. By eschewing unwarranted and unnecessary assumptions about the distribution of neural activity and instead carefully integrating information from EEG and fMRI, we are able to dramatically improve the quality of source-localization. Thus maintaining a watchful eye towards principles of optimality, while avoiding unnecessary statistical assumptions is an effective theoretical approach to neuroscience.
Wheeler, Ward C
2003-08-01
The problem of determining the minimum cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete (Wang and Jiang, 1994). Traditionally, point estimations of hypothetical ancestral sequences have been used to gain heuristic, upper bounds on cladogram cost. These include procedures with such diverse approaches as non-additive optimization of multiple sequence alignment, direct optimization (Wheeler, 1996), and fixed-state character optimization (Wheeler, 1999). A method is proposed here which, by extending fixed-state character optimization, replaces the estimation process with a search. This form of optimization examines a diversity of potential state solutions for cost-efficient hypothetical ancestral sequences and can result in greatly more parsimonious cladograms. Additionally, such an approach can be applied to other NP-complete phylogenetic optimization problems such as genomic break-point analysis. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.
Zhou, Zhi; de Bedout, Juan Manuel; Kern, John Michael; Biyik, Emrah; Chandra, Ramu Sharat
2013-01-22
A system for optimizing customer utility usage in a utility network of customer sites, each having one or more utility devices, where customer site is communicated between each of the customer sites and an optimization server having software for optimizing customer utility usage over one or more networks, including private and public networks. A customer site model for each of the customer sites is generated based upon the customer site information, and the customer utility usage is optimized based upon the customer site information and the customer site model. The optimization server can be hosted by an external source or within the customer site. In addition, the optimization processing can be partitioned between the customer site and an external source.
NASA Technical Reports Server (NTRS)
Wheeler, Ward C.
2003-01-01
The problem of determining the minimum cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete (Wang and Jiang, 1994). Traditionally, point estimations of hypothetical ancestral sequences have been used to gain heuristic, upper bounds on cladogram cost. These include procedures with such diverse approaches as non-additive optimization of multiple sequence alignment, direct optimization (Wheeler, 1996), and fixed-state character optimization (Wheeler, 1999). A method is proposed here which, by extending fixed-state character optimization, replaces the estimation process with a search. This form of optimization examines a diversity of potential state solutions for cost-efficient hypothetical ancestral sequences and can result in greatly more parsimonious cladograms. Additionally, such an approach can be applied to other NP-complete phylogenetic optimization problems such as genomic break-point analysis. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.
NASA Technical Reports Server (NTRS)
Wheeler, Ward C.
2003-01-01
The problem of determining the minimum cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete (Wang and Jiang, 1994). Traditionally, point estimations of hypothetical ancestral sequences have been used to gain heuristic, upper bounds on cladogram cost. These include procedures with such diverse approaches as non-additive optimization of multiple sequence alignment, direct optimization (Wheeler, 1996), and fixed-state character optimization (Wheeler, 1999). A method is proposed here which, by extending fixed-state character optimization, replaces the estimation process with a search. This form of optimization examines a diversity of potential state solutions for cost-efficient hypothetical ancestral sequences and can result in greatly more parsimonious cladograms. Additionally, such an approach can be applied to other NP-complete phylogenetic optimization problems such as genomic break-point analysis. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.
Transit Timing Study of Kepler Planets
NASA Astrophysics Data System (ADS)
Xie, Jiwei
2015-08-01
Kepler space telescope has found over 4000 transiting planet candidates. Transit timing is a powerful tool to study these transit planet candidates. In this talk, I will talk about two transit timing techniques, i.e., transit timing variation (TTV) and transit duration (TD), which enable confirming their planetary nature and obtaining insight into their orbital properties.
Homotopy optimization methods for global optimization.
Dunlavy, Daniel M.; O'Leary, Dianne P. (University of Maryland, College Park, MD)
2005-12-01
We define a new method for global optimization, the Homotopy Optimization Method (HOM). This method differs from previous homotopy and continuation methods in that its aim is to find a minimizer for each of a set of values of the homotopy parameter, rather than to follow a path of minimizers. We define a second method, called HOPE, by allowing HOM to follow an ensemble of points obtained by perturbation of previous ones. We relate this new method to standard methods such as simulated annealing and show under what circumstances it is superior. We present results of extensive numerical experiments demonstrating performance of HOM and HOPE.
Optimal outpatient appointment scheduling.
Kaandorp, Guido C; Koole, Ger
2007-09-01
In this paper optimal outpatient appointment scheduling is studied. A local search procedure is derived that converges to the optimal schedule with a weighted average of expected waiting times of patients, idle time of the doctor and tardiness (lateness) as objective. No-shows are allowed to happen. For certain combinations of parameters the well-known Bailey-Welch rule is found to be the optimal appointment schedule.
Conceptual design optimization study
NASA Technical Reports Server (NTRS)
Hollowell, S. J.; Beeman, E. R., II; Hiyama, R. M.
1990-01-01
The feasibility of applying multilevel functional decomposition and optimization techniques to conceptual design of advanced fighter aircraft was investigated. Applying the functional decomposition techniques to the conceptual design phase appears to be feasible. The initial implementation of the modified design process will optimize wing design variables. A hybrid approach, combining functional decomposition techniques for generation of aerodynamic and mass properties linear sensitivity derivatives with existing techniques for sizing mission performance and optimization, is proposed.
Partnership Transitions and Maternal Parenting
Beck, Audrey N.; Cooper, Carey E.; McLanahan, Sara; Brooks-Gunn, Jeanne
2011-01-01
We use data from the Fragile Families and Child Wellbeing Study (N = 1,975) to examine the association between mothers’ partnership changes and parenting behavior during the first five years of their children’s lives. We compare coresidential with dating transitions, and recent with more distal transitions. We also examine interactions between transitions and race/ethnicity, maternal education and family structure at birth. Findings indicate that both coresidential and dating transitions were associated with higher levels of maternal stress and harsh parenting; recent transitions had stronger associations than distal transitions. Maternal education significantly moderates these associations, with less educated mothers responding more negatively to instability in terms of maternal stress, and more educated mothers responding more negatively in terms of literacy activities. PMID:21423848
Optimal divergence-free inflow perturbations in flow over an airfoil
NASA Astrophysics Data System (ADS)
Loh, Sean; Blackburn, Hugh; Mao, Xuerui
2013-11-01
Linear transient growth analysis has identified various key mechanisms in transition due to free-stream turbulence in canonical flow open flow configurations (Durbin & Wu, 2007). In the present work, the role of inflow disturbances in promoting transition for flow over airfoil type geometries is examined. Using an optimal control based methodology, optimal divergence-free inflow perturbations for linear transient energy growth are computed for a NACA 0012 airfoil at 4° angle of attack. At various low-to-moderate Reynolds numbers, the flow response to optimal two-dimensional inflow perturbations with varying streamwise length scale is analysed. The relationship between the flow physics induced by optimal inflow perturbations, optimal initial perturbations and leading linear instability modes is then examined. Durbin P & Wu X (2007), Transition beneath vortical disturbances, Annu. Rev. Fluid Mech. 39: 107. Supported by Australian Research Council grant DP1094851.
Control and optimization system
Xinsheng, Lou
2013-02-12
A system for optimizing a power plant includes a chemical loop having an input for receiving an input parameter (270) and an output for outputting an output parameter (280), a control system operably connected to the chemical loop and having a multiple controller part (230) comprising a model-free controller. The control system receives the output parameter (280), optimizes the input parameter (270) based on the received output parameter (280), and outputs an optimized input parameter (270) to the input of the chemical loop to control a process of the chemical loop in an optimized manner.
Pubertal transitions in health.
Patton, George C; Viner, Russell
2007-03-31
Puberty is accompanied by physical, psychological, and emotional changes adapted to ensure reproductive and parenting success. Human puberty stands out in the animal world for its association with brain maturation and physical growth. Its effects on health and wellbeing are profound and paradoxical. On the one hand, physical maturation propels an individual into adolescence with peaks in strength, speed, and fitness. Clinicians have viewed puberty as a point of maturing out of childhood-onset conditions. However, puberty's relevance for health has shifted with a modern rise in psychosocial disorders of young people. It marks a transition in risks for depression and other mental disorders, psychosomatic syndromes, substance misuse, and antisocial behaviours. Recent secular trends in these psychosocial disorders coincide with a growing mismatch between biological and social maturation, and the emergence of more dominant youth cultures.
NASA Astrophysics Data System (ADS)
Gitterman, Moshe
2014-09-01
In discussing phase transitions, the first thing that we have to do is to define a phase. This is a concept from thermodynamics and statistical mechanics, where a phase is defined as a homogeneous system. As a simple example, let us consider instant coffee. This consists of coffee powder dissolved in water, and after stirring it we have a homogeneous mixture, i.e., a single phase. If we add to a cup of coffee a spoonful of sugar and stir it well, we still have a single phase -- sweet coffee. However, if we add ten spoonfuls of sugar, then the contents of the cup will no longer be homogeneous, but rather a mixture of two homogeneous systems or phases, sweet liquid coffee on top and coffee-flavored wet sugar at the bottom...
NASA Technical Reports Server (NTRS)
Viterna, Larry A.
1997-01-01
A government, industry, and university cooperative is developing an advanced hybrid electric city transit bus. Goals of this effort include doubling the fuel economy compared to current buses and reducing emissions to one-tenth of current EPA standards. Unique aspects of the vehicle's power system include the use of ultra-capacitors as an energy storage system, and a planned natural gas fueled turbogenerator developed from a small jet engine. Power from both the generator and energy storage system is provided to a variable speed electric motor attached to the rear axle. At over 15000 kg gross weight, this is the largest vehicle of its kind ever built using ultra-capacitor energy storage. This paper describes the overall power system architecture, the evolution of the control strategy, and its performance over industry standard drive cycles.
Nonadiabatic transition path sampling
NASA Astrophysics Data System (ADS)
Sherman, M. C.; Corcelli, S. A.
2016-07-01
Fewest-switches surface hopping (FSSH) is combined with transition path sampling (TPS) to produce a new method called nonadiabatic path sampling (NAPS). The NAPS method is validated on a model electron transfer system coupled to a Langevin bath. Numerically exact rate constants are computed using the reactive flux (RF) method over a broad range of solvent frictions that span from the energy diffusion (low friction) regime to the spatial diffusion (high friction) regime. The NAPS method is shown to quantitatively reproduce the RF benchmark rate constants over the full range of solvent friction. Integrating FSSH within the TPS framework expands the applicability of both approaches and creates a new method that will be helpful in determining detailed mechanisms for nonadiabatic reactions in the condensed-phase.
Different disciplines, different transitions
NASA Astrophysics Data System (ADS)
Wood, Leigh; Solomonides, Ian
2008-09-01
There is not just one mathematics taught at university level, nor is there one group of students. Mathematics is taught differently depending on the discipline and the perceived background of the student. There is engineering mathematics for the students heading towards engineering degrees, life science mathematics for those heading towards biology degrees and so on. This paper considers the phases of transitions that students experience as they embark on a course of study and then go on to professional life. We make inferences about the ways the curriculum should be designed to alleviate the difficulties of these phases as well as to take account of the capabilities that graduates will require in the workplace. It is not only where students are coming from that affects their learning but where they are heading to, in combination with their perceptions of that destination.
The ``Venus Transit Experience''
NASA Astrophysics Data System (ADS)
Boffin, H.; West, R.
2004-12-01
On November 5-7, 2004, an unusual conference took place at the French Ministry of Research in Paris. Entitled the “Venus Transit Experience”, this meeting was organised by the VT-2004 International Steering Committee (ISC) and the local arrangements were ably taken care of by the staff of the IMCCE and the Observatoire de Paris, with Jean-Eudes Arlot and William Thuillot at the helm. It brought together more than 150 persons connected to the VT-2004 programme. The aim was to sum up the vast experience gained through this unique public education programme and, in particular, to perform an evaluation of its many components. On the first day, more than 50 students from the Paris areas who participated actively in this programme were also present.
Mercury Transit (Composite Image)
2017-09-28
On May 9, 2016, Mercury passed directly between the sun and Earth. This event – which happens about 13 times each century – is called a transit. NASA’s Solar Dynamics Observatory, or SDO, studies the sun 24/7 and captured the entire seven-and-a-half-hour event. This composite image of Mercury’s journey across the sun was created with visible-light images from the Helioseismic and Magnetic Imager on SDO. Image Credit: NASA's Goddard Space Flight Center/SDO/Genna Duberstein NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
Transition in hypersonic boundary layers
NASA Astrophysics Data System (ADS)
Zhang, Chuanhong; Zhu, Yiding; Chen, Xi; Yuan, Huijing; Wu, Jiezhi; Chen, Shiyi; Lee, Cunbiao; Gad-el-Hak, Mohamed
2015-10-01
Transition and turbulence production in a hypersonic boundary layer is investigated in a Mach 6 wind tunnel using Rayleigh-scattering visualization, fast-response pressure measurements, and particle image velocimetry. It is found that the second-mode instability is a key modulator of the transition process. Although the second-mode is primarily an acoustic wave, it causes the formation of high-frequency vortical waves, which triggers a fast transition to turbulence.
Sharp transitions in low-number quantum dots Bayesian magnetometry
Mazurek, Paweł; Horodecki, Michał; Czekaj, Łukasz; Horodecki, Paweł
2016-01-01
We consider Bayesian estimate of static magnetic field, characterized by a prior Gaussian probability distribution, in systems of a few electron quantum dot spins interacting with infinite temperature spin environment via hyperfine interaction. Sudden transitions among optimal states and measurements are observed. Usefulness of measuring occupation levels is shown for all times of the evolution, together with the role of entanglement in the optimal scenario. For low values of magnetic field, memory effects stemming from the interaction with environment provide limited metrological advantage. PMID:27686417
Optimal control of wave-packets: a semiclassical approach
NASA Astrophysics Data System (ADS)
Darío Guerrero, Rubén; Arango, Carlos A.; Reyes, Andrés
2014-02-01
We studied the optimal quantum control of a molecular rotor in tilted laser fields using the time-sliced Herman-Kluk propagator for the evaluation of the optimal pulse and the light-dipole interaction as the control mechanism. The proposed methodology was used to study the effects of an optimal pulse on the evolution of a wave-packet in a double-well potential and in the effective potential of a molecular rotor in a collinear tilted fields setup. The amplitude and frequency of the control pulse were obtained in such a way that the transition probability between two rotational wave-packets was maximised.
Transit clairvoyance: enhancing TESS follow-up using artificial neural networks
NASA Astrophysics Data System (ADS)
Kipping, David M.; Lam, Christopher
2017-03-01
The upcoming Transiting Exoplanet Survey Satellite (TESS) mission is expected to find thousands of transiting planets around bright stars, yet for three-quarters of the fields observed the temporal coverage will limit discoveries to planets with orbital periods below 13.7 d. From the Kepler catalogue, the mean probability of these short-period transiting planets having additional longer period transiters (which would be missed by TESS) is 18 per cent, a value 10 times higher than the average star. In this work, we show how this probability is not uniform but functionally dependent upon the properties of the observed short-period transiters, ranging from less than 1 per cent up to over 50 per cent. Using artificial neural networks (ANNs) trained on the Kepler catalogue and making careful feature selection to account for the differing sensitivity of TESS, we are able to predict the most likely short-period transiters to be accompanied by additional transiters. Through cross-validation, we predict that a targeted, optimized TESS transit and/or radial velocity follow-up programme using our trained ANN would have a discovery yield improved by a factor of 2. Our work enables a near-optimal follow-up strategy for surveys following TESS targets for additional planets, improving the science yield derived from TESS and particularly beneficial in the search for habitable-zone transiting worlds.
Empirical Investigation of Critical Transitions in Paleoclimate
NASA Astrophysics Data System (ADS)
Loskutov, E. M.; Mukhin, D.; Gavrilov, A.; Feigin, A.
2016-12-01
In this work we apply a new empirical method for the analysis of complex spatially distributed systems to the analysis of paleoclimate data. The method consists of two general parts: (i) revealing the optimal phase-space variables and (ii) construction the empirical prognostic model by observed time series. The method of phase space variables construction based on the data decomposition into nonlinear dynamical modes which was successfully applied to global SST field and allowed clearly separate time scales and reveal climate shift in the observed data interval [1]. The second part, the Bayesian approach to optimal evolution operator reconstruction by time series is based on representation of evolution operator in the form of nonlinear stochastic function represented by artificial neural networks [2,3]. In this work we are focused on the investigation of critical transitions - the abrupt changes in climate dynamics - in match longer time scale process. It is well known that there were number of critical transitions on different time scales in the past. In this work, we demonstrate the first results of applying our empirical methods to analysis of paleoclimate variability. In particular, we discuss the possibility of detecting, identifying and prediction such critical transitions by means of nonlinear empirical modeling using the paleoclimate record time series. The study is supported by Government of Russian Federation (agreement #14.Z50.31.0033 with the Institute of Applied Physics of RAS). 1. Mukhin, D., Gavrilov, A., Feigin, A., Loskutov, E., & Kurths, J. (2015). Principal nonlinear dynamical modes of climate variability. Scientific Reports, 5, 15510. http://doi.org/10.1038/srep155102. Ya. I. Molkov, D. N. Mukhin, E. M. Loskutov, A.M. Feigin, (2012) : Random dynamical models from time series. Phys. Rev. E, Vol. 85, n.3.3. Mukhin, D., Kondrashov, D., Loskutov, E., Gavrilov, A., Feigin, A., & Ghil, M. (2015). Predicting Critical Transitions in ENSO models. Part II
Health Care Transition Experiences of Young Adults With Cerebral Palsy.
Carroll, Ellen McLaughlin
2015-01-01
Health care transition (HCT) describes the purposeful, planned movement of adolescents from child to adult-orientated care. The purpose of this qualitative study is to uncover the meaning of transition to adult-centered care as experienced by young adults with cerebral palsy (YA-CP) through the research question: What are the lived experiences of young adults with cerebral palsy transitioning from pediatric to adult healthcare? Six females and 3 males, aged 19-25 years of age, who identified as carrying the diagnosis of cerebral palsy without cognitive impairment, were interviewed. Giorgi's (1985) method for analysis of phenomenology was the framework for the study and guided the phenomenological reduction. The meaning of the lived experiences of YA-CPs transition to adult health care is expert novices with evidence and experience-based expectations, negotiating new systems interdependently and accepting less than was expected. More information and support is needed for the YA-CP during transition to ensure a well-organized move to appropriate adult-oriented health care that is considerate of the lifelong impact of the disorder. The nurses' role as advocate, mentor and guide can optimize the individual's response to the transition process.
Quantum phase transition in space
Damski, Bogdan; Zurek, Wojciech H
2008-01-01
A quantum phase transition between the symmetric (polar) phase and the phase with broken symmetry can be induced in a ferromagnetic spin-1 Bose-Einstein condensate in space (rather than in time). We consider such a phase transition and show that the transition region in the vicinity of the critical point exhibits scalings that reflect a compromise between the rate at which the transition is imposed (i.e., the gradient of the control parameter) and the scaling of the divergent healing length in the critical region. Our results suggest a method for the direct measurement of the scaling exponent {nu}.
Transit satellite system timing capabilities
NASA Technical Reports Server (NTRS)
Finsod, T. D.
1978-01-01
Current time transfer capabilities of the Transit Satellite System are reviewed. Potential improvements in the changes in equipment and operational procedures using operational satellites are discussed.
Transition research using flight experiments
NASA Technical Reports Server (NTRS)
Reshotko, Eli
1990-01-01
The paper deals with flight experiments as a means of obtaining proper transition information in an uncontaminated environment. Flight transition experiments performed in the early to middle 1950s using rocket-propelled vehicles are outlined. It is noted that the standards for research quality experiments on stability and transition are no different for flight studies than for wind-tunnel experiments. The guidelines formulated by the U.S. Boundary Layer Transition Study Group are listed. Attention is focused on the relationship between the model design and the measurement of disturbance environment, the maintenance and monitoring of test and model-surface conditions, and a need for high data-sampling rates.
Transit administration and planning research
de Corla-Souza; Gupta.
1989-01-01
The 10 papers in the report deal with the following areas: Evaluation of demand-management strategies for Toledo's year 2010 transportation plan; Accommodating deaf and hard-of-hearing persons on public transportation systems in Massachusetts; Quick approach to compare highway and bus transit alternatives using the arterial analysis package; Panel survey approach to measuring transit route service elasticity of demand; UMTA and major investments: evaluation process and results; Using early performance to project transit route ridership: comparison of methods; Institutional requirements for competition: labor issues; Updating ride checks with multiple point checks; Producing section 15 service-consumed data: challenge for large transit; Parkrose targeted marketing campaign pass-incentive program.
Transition Metal Compounds Towards Holography
Dieckmann, Volker; Eicke, Sebastian; Springfeld, Kristin; Imlau, Mirco
2012-01-01
We have successfully proposed the application of transition metal compounds in holographic recording media. Such compounds feature an ultra-fast light-induced linkage isomerization of the transition-metal–ligand bond with switching times in the sub-picosecond regime and lifetimes from microseconds up to hours at room temperature. This article highlights the photofunctionality of two of the most promising transition metal compounds and the photophysical mechanisms that are underlying the hologram recording. We present the latest progress with respect to the key measures of holographic media assembled from transition metal compounds, the molecular embedding in a dielectric matrix and their impressive potential for modern holographic applications. PMID:28817028
Diverse types of percolation transitions
NASA Astrophysics Data System (ADS)
Lee, Deokjae; Cho, Y. S.; Kahng, B.
2016-12-01
Percolation has long served as a model for diverse phenomena and systems. The percolation transition, that is, the formation of a giant cluster on a macroscopic scale, is known as one of the most robust continuous transitions. Recently, however, many abrupt percolation transitions have been observed in complex systems. To illustrate such phenomena, considerable effort has been made to introduce models and construct theoretical frameworks for explosive, discontinuous, and hybrid percolation transitions. Experimental results have also been reported. In this review article, we describe such percolation models, their critical behaviors and universal features, and real-world phenomena.
[Sleep-wake transition disorders].
Honma, H; Kobayashi, R; Koyama, T
1998-02-01
The term sleep-wake transition disorders refers to a group of parasomnias that occur during the transition from wakefulness to sleep or from one sleep stage to another. Rhythmic movement disorder, sleep starts, sleep talking, and nocturnal leg cramps--these four disorders belong to sleep-wake transition disorders in the International Classification of Sleep Disorders. Although these are common disorders, little attention is given to them and their mechanisms are remain unclear. The majority of patients are not so severe as to require any treatment. Their prognosis are usually well. This article describes sleep-wake transition disorders concerning the clinical features, differential diagnosis, treatment, etc.
Transitions to Least Restrictive Environments: A Guide to Transition. Revised.
ERIC Educational Resources Information Center
Beninghof, Anne M.
This guide to the transition of special education students to less restrictive environments or from school to work stresses the importance of planning and communication during the entire process, from initial plans through implementation and follow-up. Section 1 consists of a "Transition Process Checklist" to aid in the organization and follow…
Essentials of Transition Planning. Brookes Transition to Adulthood Series
ERIC Educational Resources Information Center
Wehman, Paul
2011-01-01
For young people with disabilities, crossing the bridge to adulthood will be empowering instead of intimidating--when their support teams know the essentials of effective transition planning. Now all the fundamentals of well-crafted transition plans are collected in one concise quick-guide, straight from one of the top authorities on helping young…
Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Preliminary Evaluation Results
Chandler, K.; Eudy, L.
2008-10-01
This report provides preliminary results from a National Renewable Energy Laboratory evaluation of a protoptye fuel cell transit bus operating at Connecticut Transit in Hartford. Included are descriptions of the planned fuel cell bus demonstration and equipment; early results and agency experience are also provided.
Essentials of Transition Planning. Brookes Transition to Adulthood Series
ERIC Educational Resources Information Center
Wehman, Paul
2011-01-01
For young people with disabilities, crossing the bridge to adulthood will be empowering instead of intimidating--when their support teams know the essentials of effective transition planning. Now all the fundamentals of well-crafted transition plans are collected in one concise quick-guide, straight from one of the top authorities on helping young…
High-Fidelity Aerodynamic Shape Optimization for Natural Laminar Flow
NASA Astrophysics Data System (ADS)
Rashad, Ramy
To ensure the long-term sustainability of aviation, serious effort is underway to mitigate the escalating economic, environmental, and social concerns of the industry. Significant improvement to the energy efficiency of air transportation is required through the research and development of advanced and unconventional airframe and engine technologies. In the quest to reduce airframe drag, this thesis is concerned with the development and demonstration of an effective design tool for improving the aerodynamic efficiency of subsonic and transonic airfoils. The objective is to advance the state-of-the-art in high-fidelity aerodynamic shape optimization by incorporating and exploiting the phenomenon of laminar-turbulent transition in an efficient manner. A framework for the design and optimization of Natural Laminar Flow (NLF) airfoils is developed and demonstrated with transition prediction capable of accounting for the effects of Reynolds number, freestream turbulence intensity, Mach number, and pressure gradients. First, a two-dimensional Reynolds-averaged Navier-Stokes (RANS) flow solver has been extended to incorporate an iterative laminar-turbulent transition prediction methodology. The natural transition locations due to Tollmien-Schlichting instabilities are predicted using the simplified eN envelope method of Drela and Giles or, alternatively, the compressible form of the Arnal-Habiballah-Delcourt criterion. The boundary-layer properties are obtained directly from the Navier-Stokes flow solution, and the transition to turbulent flow is modeled using an intermittency function in conjunction with the Spalart-Allmaras turbulence model. The RANS solver is subsequently employed in a gradient-based sequential quadratic programming shape optimization framework. The laminar-turbulent transition criteria are tightly coupled into the objective and gradient evaluations. The gradients are obtained using a new augmented discrete-adjoint formulation for non-local transition
Ant groups optimally amplify the effect of transiently informed individuals.
Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Ghosh, Abhijit; Gov, Nir; Feinerman, Ofer
2015-07-28
To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge.
Ant groups optimally amplify the effect of transiently informed individuals
Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Ghosh, Abhijit; Gov, Nir; Feinerman, Ofer
2015-01-01
To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge. PMID:26218613
Ant groups optimally amplify the effect of transiently informed individuals
NASA Astrophysics Data System (ADS)
Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Ghosh, Abhijit; Gov, Nir; Feinerman, Ofer
2015-07-01
To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge.
Lost in Transition: Examining Transitions in Psychotherapy Training.
Tan, Adrienne; Philipp, Diane; Malat, Jan; Feder, Victor; Kulkarni, Chetana; Lawson, Andrea; So, Vivien; Ravitz, Paula
2015-10-01
Disruptions are inevitable during psychiatry residency training and can affect resident learning and patient care. This exploratory study examined the nature and impact of transitions in psychotherapy training. PGY2-5 residents (45/150; 30% response rate) and psychotherapy supervisors (46/247; 18.6% response rate) were surveyed about transitional events during residency training in psychotherapy. Supervisors and residents ranked the frequency of occurrence of transitional events and their impact very similarly, as well as the "feed forward" items when transitioning to a new supervisor. Residents feeling confused or overwhelmed with the balancing of learning differing models with differing levels of comfort or knowledge was ranked as the issue that occurred most frequently by both supervisors and residents. This study highlights issues that arise at transitions during psychotherapy training in psychiatry residency. Strategies for managing these periods are discussed, with a focus on resident learning and improved continuity of patient care.
Implementing optimal thinning strategies
Kurt H. Riitters; J. Douglas Brodie
1984-01-01
Optimal thinning regimes for achieving several management objectives were derived from two stand-growth simulators by dynamic programming. Residual mean tree volumes were then plotted against stand density management diagrams. The results supported the use of density management diagrams for comparing, checking, and implementing the results of optimization analyses....
Elastic swimming I: Optimization
NASA Astrophysics Data System (ADS)
Lauga, Eric; Yu, Tony; Hosoi, Anette
2006-03-01
We consider the problem of swimming at low Reynolds number by oscillating an elastic filament in a viscous liquid, as investigated by Wiggins and Goldstein (1998, Phys Rev Lett). In this first part of the study, we characterize the optimal forcing conditions of the swimming strategy and its optimal geometrical characteristics.
Phase transitions in disordered systems
NASA Astrophysics Data System (ADS)
Hrahsheh, Fawaz Y.
Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A1-xBx. Our results show that the disorder completely destroys the phase transition with a pronounced tail of the ordered phase developing for all compositions x < 1. In addition, we find that short-ranged disorder correlations can have a dramatic effect on the transition. Moreover, we show an experimental realization of the composition-tuned ferromagnetic-to-paramagnetic quantum phase transition in Sr1-xCa xRuO3. We investigate the effects of disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong disorder renormalization group, we demonstrate that disorder rounds the first-order transition to a continuous one for both weak and strong coupling between the colors. Finally, we investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte-Carlo simulations. Beyond a critical disorder strength, we find nonuniversal, disorder dependent critical behavior.
Light Scattering in Exoplanet Transits
NASA Astrophysics Data System (ADS)
Robinson, Tyler D.; Fortney, Jonathan J.
2016-10-01
Transit spectroscopy is currently the leading technique for studying exoplanet atmospheric composition, and has led to the detection of molecular species, clouds, and/or hazes for numerous worlds outside the Solar System. The field of exoplanet transit spectroscopy will be revolutionized with the anticipated launch of NASA's James Webb Space Telescope (JWST) in 2018. Over the course of the design five year mission for JWST, the observatory is expected to provide in-depth observations of many tens of transiting exoplanets, including some worlds in the poorly understood 2-4 Earth-mass regime. As the quality of transit spectrum observations continues to improve, so should models of exoplanet transits. Thus, certain processes initially thought to be of second-order importance should be revisited and possibly added to modeling tools. For example, atmospheric refraction, which was commonly omitted from early transit spectrum models, has recently been shown to be of critical importance in some terrestrial exoplanet transits. Beyond refraction, another process that has seen little study with regards to exoplanet transits is light multiple scattering. In most cases, scattering opacity in exoplanet transits has been treated as equivalent to absorption opacity. However, this equivalence cannot always hold, such as in the case of a strongly forward scattering, weakly absorbing aerosol. In this presentation, we outline a theory of exoplanet transit spectroscopy that spans the geometric limit (used in most modern models) to a fully multiple scattering approach. We discuss a new technique for improving model efficiency that effectively separates photon paths, which tend to vary slowly in wavelength, from photon absorption, which can vary rapidly in wavelength. Using this newly developed approach, we explore situations where cloud or haze scattering may be important to JWST observations of gas giants, and comment on the conditions necessary for scattering to become a major
Optimal Disturbances in Boundary Layers Subject to Streamwise Pressure Gradient
NASA Technical Reports Server (NTRS)
Tumin, Anatoli; Ashpis, David E.
2003-01-01
Laminar-turbulent transition in shear flows is still an enigma in the area of fluid mechanics. The conventional explanation of the phenomenon is based on the instability of the shear flow with respect to infinitesimal disturbances. The conventional hydrodynamic stability theory deals with the analysis of normal modes that might be unstable. The latter circumstance is accompanied by an exponential growth of the disturbances that might lead to laminar-turbulent transition. Nevertheless, in many cases, the transition scenario bypasses the exponential growth stage associated with the normal modes. This type of transition is called bypass transition. An understanding of the phenomenon has eluded us to this day. One possibility is that bypass transition is associated with so-called algebraic (non-modal) growth of disturbances in shear flows. In the present work, an analysis of the optimal disturbances/streamwise vortices associated with the transient growth mechanism is performed for boundary layers in the presence of a streamwise pressure gradient. The theory will provide the optimal spacing of the control elements in the spanwise direction and their placement in the streamwise direction.
Rapid Mars transits with exhaust-modulated plasma propulsion
NASA Technical Reports Server (NTRS)
Chang-Diaz, Franklin R.; Braden, Ellen; Johnson, Ivan; Hsu, Michael M.; Yang, Tien Fang
1995-01-01
The operational characteristics of the Exhaust-Modulated Plasma Rocket are described. Four basic human and robotic mission scenarios to Mars are analyzed using numerical optimization techniques at variable specific impulse and constant power. The device is well suited for 'split-sprint' missions, allowing fast, one-way low-payload human transits of 90 to 104 days, as well as slower, 180-day, high-payload robotic precursor flights. Abort capabilities, essential for human missions, are also explored.
Transitions in the Communication Capacity of Dissipative Qubit Channels
NASA Astrophysics Data System (ADS)
Daems, D.
2009-05-01
The information transmission is studied for quantum channels in which the noise includes dissipative effects, more specifically, nonunitality. Noise is usually a nuisance but can sometimes be helpful. For these channels, the communication capacity is shown to increase with the dissipative component of the noise and may exhibit transitions beyond which it increases faster. The optimal states are constructed analytically as well as the pertaining “phase” diagram.
Transition state theory: Variational formulation, dynamical corrections, and error estimates
NASA Astrophysics Data System (ADS)
Vanden-Eijnden, Eric; Tal, Fabio A.
2005-11-01
Transition state theory (TST) is revisited, as well as evolutions upon TST such as variational TST in which the TST dividing surface is optimized so as to minimize the rate of recrossing through this surface and methods which aim at computing dynamical corrections to the TST transition rate constant. The theory is discussed from an original viewpoint. It is shown how to compute exactly the mean frequency of transition between two predefined sets which either partition phase space (as in TST) or are taken to be well-separated metastable sets corresponding to long-lived conformation states (as necessary to obtain the actual transition rate constants between these states). Exact and approximate criterions for the optimal TST dividing surface with minimum recrossing rate are derived. Some issues about the definition and meaning of the free energy in the context of TST are also discussed. Finally precise error estimates for the numerical procedure to evaluate the transmission coefficient κS of the TST dividing surface are given, and it is shown that the relative error on κS scales as 1/√κS when κS is small. This implies that dynamical corrections to the TST rate constant can be computed efficiently if and only if the TST dividing surface has a transmission coefficient κS which is not too small. In particular, the TST dividing surface must be optimized upon (for otherwise κS is generally very small), but this may not be sufficient to make the procedure numerically efficient (because the optimal dividing surface has maximum κS, but this coefficient may still be very small).
Optimal synchronization in space.
Brede, Markus
2010-02-01
In this Rapid Communication we investigate spatially constrained networks that realize optimal synchronization properties. After arguing that spatial constraints can be imposed by limiting the amount of "wire" available to connect nodes distributed in space, we use numerical optimization methods to construct networks that realize different trade offs between optimal synchronization and spatial constraints. Over a large range of parameters such optimal networks are found to have a link length distribution characterized by power-law tails P(l) proportional to l(-alpha), with exponents alpha increasing as the networks become more constrained in space. It is also shown that the optimal networks, which constitute a particular type of small world network, are characterized by the presence of nodes of distinctly larger than average degree around which long-distance links are centered.
Optimal Limited Contingency Planning
NASA Technical Reports Server (NTRS)
Meuleau, Nicolas; Smith, David E.
2003-01-01
For a given problem, the optimal Markov policy over a finite horizon is a conditional plan containing a potentially large number of branches. However, there are applications where it is desirable to strictly limit the number of decision points and branches in a plan. This raises the question of how one goes about finding optimal plans containing only a limited number of branches. In this paper, we present an any-time algorithm for optimal k-contingency planning. It is the first optimal algorithm for limited contingency planning that is not an explicit enumeration of possible contingent plans. By modelling the problem as a partially observable Markov decision process, it implements the Bellman optimality principle and prunes the solution space. We present experimental results of applying this algorithm to some simple test cases.
Algorithms for bilevel optimization
NASA Technical Reports Server (NTRS)
Alexandrov, Natalia; Dennis, J. E., Jr.
1994-01-01
General multilevel nonlinear optimization problems arise in design of complex systems and can be used as a means of regularization for multi-criteria optimization problems. Here, for clarity in displaying our ideas, we restrict ourselves to general bi-level optimization problems, and we present two solution approaches. Both approaches use a trust-region globalization strategy, and they can be easily extended to handle the general multilevel problem. We make no convexity assumptions, but we do assume that the problem has a nondegenerate feasible set. We consider necessary optimality conditions for the bi-level problem formulations and discuss results that can be extended to obtain multilevel optimization formulations with constraints at each level.
Optimal synchronization in space
NASA Astrophysics Data System (ADS)
Brede, Markus
2010-02-01
In this Rapid Communication we investigate spatially constrained networks that realize optimal synchronization properties. After arguing that spatial constraints can be imposed by limiting the amount of “wire” available to connect nodes distributed in space, we use numerical optimization methods to construct networks that realize different trade offs between optimal synchronization and spatial constraints. Over a large range of parameters such optimal networks are found to have a link length distribution characterized by power-law tails P(l)∝l-α , with exponents α increasing as the networks become more constrained in space. It is also shown that the optimal networks, which constitute a particular type of small world network, are characterized by the presence of nodes of distinctly larger than average degree around which long-distance links are centered.
Universal deblurring method for real images using transition region
NASA Astrophysics Data System (ADS)
Hong, Hanyu; Li, Liangcheng; Park, In Kyu; Zhang, Tianxu
2012-04-01
In this paper, we present a universal deblurring method for real images without prior knowledge of the blur source. The proposed method uses the transition region of the blurred image to estimate the point spread function (PSF). It determines the main edges of the blurred image with high edge measures based on the difference of Gaussians (DoG) operator. Those edge measures are used to predict the transition region of the sharp image. By using the transition region, we select the pixels of the blurred image to form a series of equations for calculating the PSF. In order to overcome noise disturbance, the optimal method based on the anisotropic adaptive regularization is used to estimate the PSF, in which the constraints of non-negative and spatial correlations are incorporated. Once the PSF is estimated, the blurred image is effectively recovered by employing nonblind restoration. Experimental results show that the proposed method performs effectively for real images with different blur sources.
Case report: microcystic transitional cell carcinoma of the urinary bladder.
Radopoulos, Demetrios; Kalyvas, Konstantinos; Kotakidou, Rodi; Panagiotopoulou, Konstantina; Katsikas, Vasilios; Papathanasiou, Michalis
2005-01-01
We report a rare case of microcystic transitional cell carcinoma involving the urinary bladder, in a 38-year-old man, and we add our experience in the treatment of this neoplasm. The tumor was muscle invasive, and a radical cystectomy was performed. The patient received no postoperative chemotherapy or radiotherapy, and he has not signs of local recurrence or distal metastasis after 3 years of intense follow up. Even though the number of cases documented so far, is insufficient to draw safe conclusions regarding the optimal treatment of the microcystic variant of transitional cell carcinoma. Our case indicates that even in cases of microcystic transitional cell carcinoma with infiltrative nature, aggressive therapy is associated with good control of the disease locally and distally.
Efficient softest mode finding in transition states calculations.
Leng, Jing; Gao, Weiguo; Shang, Cheng; Liu, Zhi-Pan
2013-03-07
Transition states are fundamental to understanding the reaction dynamics qualitatively in chemical physics. To date various methods of first principle location of the transition states have been developed. In the absence of the knowledge of the final structure, the softest-mode following method climbs up to a transition state without calculating the Hessian matrix. One weakness of this kind of approaches is that the number of rotations to determine the softest mode is usually unpredictable. In this paper, we propose a locally optimal search direction finding algorithm, namely LOR, which is an extension of the traditional conjugate gradient method without additional calculations of the forces. We also show that the translation of forces improves the numerical stability. Experiments for the Baker test system show that the proposed algorithm is much faster than the original dimer conjugate gradient method.
Catalytic mechanism of transition-metal compounds on Mg hydrogen sorption reaction.
Barkhordarian, Gagik; Klassen, Thomas; Bormann, Rüdiger
2006-06-08
The catalytic mechanisms of transition-metal compounds during the hydrogen sorption reaction of magnesium-based hydrides were investigated through relevant experiments. Catalytic activity was found to be influenced by four distinct physico-thermodynamic properties of the transition-metal compound: a high number of structural defects, a low stability of the compound, which however has to be high enough to avoid complete reduction of the transition metal under operating conditions, a high valence state of the transition-metal ion within the compound, and a high affinity of the transition-metal ion to hydrogen. On the basis of these results, further optimization of the selection of catalysts for improving sorption properties of magnesium-based hydrides is possible. In addition, utilization of transition-metal compounds as catalysts for other hydrogen storage materials is considered.
Design optimization of a magnetorheological brake in powered knee orthosis
NASA Astrophysics Data System (ADS)
Ma, Hao; Liao, Wei-Hsin
2015-04-01
Magneto-rheological (MR) fluids have been utilized in devices like orthoses and prostheses to generate controllable braking torque. In this paper, a flat shape rotary MR brake is designed for powered knee orthosis to provide adjustable resistance. Multiple disk structure with interior inner coil is adopted in the MR brake configuration. In order to increase the maximal magnetic flux, a novel internal structure design with smooth transition surface is proposed. Based on this design, a parameterized model of the MR brake is built for geometrical optimization. Multiple factors are considered in the optimization objective: braking torque, weight, and, particularly, average power consumption. The optimization is then performed with Finite Element Analysis (FEA), and the optimal design is obtained among the Pareto-optimal set considering the trade-offs in design objectives.
Detection by Transit Photometry
NASA Technical Reports Server (NTRS)
Borucki, William J.; Koch, David G.; Jenkins, Jon M.; DeVincenzi, D. (Technical Monitor)
2002-01-01
A periodic sequence of planetary transits provides a valid detection of an orbiting planet and provides the relative size of the planet and its orbital period. Ancillary measurements of the stellar spectrum and the variations of the star's radial velocity or position combined with stellar models allow the absolute size of the planet and its mass to be obtained. The results of this approach have already shown that the planet orbiting HD209458 has only 70% of the mass of Jupiter, but is nearly 50% larger in radius. Based on models of planetary structure, these results imply that the planet must have spent most of its lifetime so close to the star that it has not been able to cool and contract as have the giant planets in our Solar System. Thus its density is much less than Jupiter and Saturn and is actually less than that of water; i.e., about 0.4 gr/cu cm. If more sensitive measurements of the light curve of stars with closely orbiting planets can be made that provide the varying amplitude of the light reflected by the planet at various phases in its orbit, then characteristics of the planetary atmosphere can be obtained. Potentially, these data can identify major molecular species present in the atmosphere and tell us if clouds are present and yield the phase function of the aerosols. Although such detail cannot be obtained for Earth-size planets because their signal amplitudes are too small, it is possible to get data critical to the determination of the structure of extrasolar planetary systems. In particular, the size distributions and their orbital distributions can be measured by the transit photometry missions now in development. The COROT mission should be able to find large terrestrial planets in short-period orbits while the more ambitious Kepler and Eddington missions should be able to detect planets even smaller than the Earth and at orbital distances that place them in the habitable zone of their stars.